Touch screen calibration and update methods

ABSTRACT

A method of calibrating optical components in a light-based touch screen, including providing (i) a display, (ii) a row of light pulse emitters that sequentially transmit light pulses over the display according to calibrated pulse current and pulse duration controls, and (iii) a row of light pulse receivers that receive the light pulses and that output values representing the received light pulses, each receiver having expected values for emitter-receiver pairs when the light pulses are not blocked, determining if each receiver output value for a receiver-emitter pair is within a respective designated range from the corresponding receiver expected value, and when a receiver output value for a receiver-emitter pair is outside the designated range, recalibrating the emitter, including adjusting at least one of the emitter pulse current and pulse duration such that subsequent receiver output values are within the designated range, and updating the receiver expected value for the receiver-emitter pair based on subsequent output values of the receiver.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims priority benefit of the following five U.S.provisional patent applications, the disclosures of which are herebyincorporated herein by reference.

-   -   U.S. Provisional Application No. 61/317,255, entitled OPTICAL        TOUCH SCREEN WITH WIDE BEAM TRANSMITTERS AND RECEIVERS, filed on        Mar. 24, 2010 by inventor Magnus Goertz;    -   U.S. Provisional Application No. 61/317,257, entitled OPTICAL        TOUCH SCREEN USING A MIRROR IMAGE FOR DETERMINING        THREE-DIMENSIONAL POSITION INFORMATION, filed on Mar. 24, 2010        by inventor Magnus Goertz;    -   U.S. Provisional Application No. 61/379,012, entitled OPTICAL        TOUCH SCREEN SYSTEMS USING REFLECTED LIGHT, filed on Sep. 1,        2010 by inventors Magnus Goertz, Thomas Eriksson, Joseph Shain,        Anders Jansson, Niklas Kvist and Robert Pettersson;    -   U.S. Provisional Application No. 61/380,600, entitled OPTICAL        TOUCH SCREEN SYSTEMS USING REFLECT LIGHT, filed on Sep. 7, 2010        by inventors Magnus Goertz, Thomas Eriksson, Joseph Shain,        Anders Jansson, Niklas Kvist and Robert Pettersson; and    -   U.S. Provisional Application No. 61/410,930, entitled OPTICAL        TOUCH SCREEN SYSTEMS USING REFLECT LIGHT, filed on Nov. 7, 2010        by inventors Magnus Goertz, Thomas Eriksson, Joseph Shain,        Anders Jansson, Niklas Kvist, Robert Pettersson and Lars Sparf.    -   This application is a continuation of U.S. Application No.        13/052,511, entitled LIGHT-BASED TOUCH SCREEN WITH SHIFT-ALIGNED        EMITTER AND RECEIVER LENSES, filed on Mar. 21, 2011 by inventors        Magnus Goertz, Thomas Eriksson, Joseph Shain, Anders Jamsson,        Niklas Kvist, Robert Pettersson, Lars Sparf and John Karlsson.

This application is a continuation-in-part of the following five U.S.patent applications, the disclosures of which are also herebyincorporated herein by reference.

-   -   U.S. application Ser. No. 12/371,609, entitled LIGHT-BASED TOUCH        SCREEN, filed on Feb. 15, 2009 by inventors Magnus Goertz,        Thomas Eriksson and Joseph Shain, which is a        continuation-in-part of U.S. application Ser. No. 10/494,055,        entitled ON A SUBSTRATE FORMED OR RESTING DISPLAY ARRANGEMENT,        filed on Apr. 29, 2004 by inventor Magnus Goertz, which is a        national phase of PCT Application No. PCT/SE02/02000, entitled        ON A SUBSTRATE FORMED OR RESTING DISPLAY ARRANGEMENT, filed on        Nov. 4, 2002 by inventor Magnus Goertz, which claims priority        from Swedish Application No. 0103835-5, entitled PEKSKÄRM FÖR        MOBILETELEFON REALISERAD AV DISPLAYENHET MED LJUSSÄNDANDE, filed        on Nov. 2, 2001 by inventor Magnus Goertz;    -   U.S. application Ser. No. 12/486,033, entitled USER INTERFACE        FOR MOBILE COMPUTER UNIT, filed on Jun. 17, 2009 by inventors        Magnus Goertz and Joseph Shain, which is a continuation-in-part        of U.S. application Ser. No. 10/315,250, filed on Dec. 10, 2002        by inventor Magnus Goertz, and which claims priority from U.S.        Provisional Application No. 61/132,469, entitled IMPROVED KAYPAD        FOR CHINESE CHARACTERS, filed on Jun. 19, 2008 by inventors        Magnus Goertz, Robert Pettersson, Staffan Gustafsson and Johann        Gerell;    -   U.S. application Ser. No. 12/667,692, entitled SCANNING OF A        TOUCH SCREEN, filed on Jan. 5, 2010 by inventor Magnus Goertz,        which is a national phase application of PCT Application No.        PCT/SE2007/050508, entitled SCANNING OF A TOUCH SCREEN, filed on        Jul. 6, 2007 by inventor Magnus Goertz;    -   U.S. application Ser. No. 12/760,567, entitled OPTICAL TOUCH        SCREEN SYSTEMS USING REFLECTED LIGHT, filed on Apr. 15, 2010 by        inventors Magnus Goertz, Thomas Eriksson and Joseph Shain, which        claims priority from U.S. Provisional Application No.        61/169,779, entitled OPTICAL TOUCH SCREEN, filed on Apr. 16,        2009 by inventors Magnus Goertz, Thomas Eriksson and Joseph        Shain, and from U.S. Provisional Application No. 61/171,464,        entitled TOUCH SCREEN USER INTERFACE, filed on Apr. 22, 2009 by        inventor Magnus Goertz, and from U.S. Provisional Application        No. 61/317,255 entitled OPTICAL TOUCH SCREEN WITH WIDE BEAM        TRANSMITTERS AND RECEIVERS, filed on Mar. 24, 2010 by inventor        Magnus Goertz; and    -   U.S. application Ser. No. 12/760,568, entitled OPTICAL TOUCH        SCREEN SYSTEMS USING WIDE LIGHT BEAMS, filed on Apr. 15, 2010 by        inventors Magnus Goertz, Thomas Eriksson and Joseph Shain, which        claims priority from U.S. Provisional Application No.        61/169,779, entitled OPTICAL TOUCH SCREEN, filed on Apr. 16,        2009 by inventors Magnus Goertz, Thomas Eriksson and Joseph        Shain, and from U.S. Provisional Application No. 61/171,464,        entitled TOUCH SCREEN USER INTERFACE, filed on Apr. 22, 2009 by        inventor Magnus Goertz, and from U.S. Provisional Application        No. 61/317,255 entitled OPTICAL TOUCH SCREEN WITH WIDE BEAM        TRANSMITTERS AND RECEIVERS, filed on Mar. 24, 2010 by inventor        Magnus Goertz.

FIELD OF THE INVENTION

The field of the present invention is light-based touch screens.

BACKGROUND OF THE INVENTION

Many consumer electronic devices are now being built with touchsensitive screens, for use with finger or stylus touch user inputs.These devices range from small screen devices such as mobile phones andcar entertainment systems, to mid-size screen devices such as notebookcomputers, to large screen devices such as check-in stations atairports.

Most conventional touch screen systems are based on resistive orcapacitive layers. Such systems are not versatile enough to offer anall-encompassing solution, as they are not easily scalable.

Reference is made to FIG. 1, which is a prior art illustration of aconventional touch screen system. Such systems include an LCD displaysurface 606, a resistive or capacitive overlay 801 that is placed overthe LCD surface, and a controller integrated circuit (IC) 701 thatconnects to the overlay and converts inputs from the overlay tomeaningful signals. A host device (not shown), such as a computer,receives the signals from controller IC 701, and a device driver or suchother program interprets the signals to detect a touch-based input suchas a key press or scroll movement.

Reference is made to FIG. 2, which is a prior art illustration of aconventional resistive touch screen. Shown in FIG. 2 are conductive andresistive layers 802 separated by thin spaces. A PET film 803 overlays atop circuit layer 804, which overlays a conductive coating 806.Similarly, a conductive coating 807 with spacer dots 808 overlays abottom circuit layer 805, which overlays a glass layer 607. When apointer 900, such as a finger or a stylus, touches the screen, a contactis created between resistive layers, closing a switch. A controller 701determines the current between layers to derive the position of thetouch point.

Advantages of resistive touch screens are their low cost, low powerconsumption and stylus support.

A disadvantage of resistive touch screens is that as a result of theoverlay, the screens are not fully transparent. Another disadvantage isthat pressure is required for touch detection; i.e., a pointer thattouches the screen without sufficient pressure goes undetected. As aconsequence, resistive touch screens do not detect finger touches well.Another disadvantage is that resistive touch screens are generallyunreadable in direct sunlight. Another disadvantage is that resistivetouch screens are sensitive to scratches. Yet another disadvantage isthat resistive touch screens are unable to discern that two or morepointers are touching the screen simultaneously, referred to as“multi-touch”.

Reference is made to FIG. 3, which is a prior art illustration of aconventional surface capacitive touch screen. Shown in FIG. 3 is a touchsurface 809 overlaying a coated glass substrate 810. Two sides of aglass 811 are coated with a uniform conductive indium in oxide (ITO)coating 812. In addition, a silicon dioxide hard coating 813 is coatedon the front side of one of the ITO coating layers 812. Electrodes 814are attached at the four corners of the glass, for generating anelectric current. A pointer 900, such as a finger or a stylus, touchesthe screen, and draws a small amount of current to the point of contact.A controller 701 then determines the location of the touch point basedon the proportions of current passing through the four electrodes.

Advantages of surface capacitive touch screens are finger touch supportand a durable surface.

A disadvantage of surface capacitive touch screens is that as a resultof the overlay, the screens are not fully transparent. Anotherdisadvantage is a limited temperature range for operation. Anotherdisadvantage is a limited capture speed of pointer movements, due to thecapacitive nature of the touch screens. Another disadvantage is thatsurface capacitive touch screens are susceptible to radio frequency (RF)interference and electromagnetic (EM) interference. Another disadvantageis that the accuracy of touch location determination depends on thecapacitance. Another disadvantage is that surface capacitive touchscreens cannot be used with gloves. Another disadvantage is that surfacecapacitive touch screens require a large screen border. As aconsequence, surface capacitive touch screens cannot be used with smallscreen devices. Yet another disadvantage is that surface capacitivetouch screens are unable to discern a mufti-touch.

Reference is made to FIG. 4, which is a prior art illustration of aconventional projected capacitive touch screen. Shown in FIG. 4 areetched ITO layers 815 that form multiple horizontal (x-axis) andvertical (y-axis) electrodes. Etched layers 815 include outer hard coatlayers 816 and 817, an x-axis electrode pattern 818, a y-axis electrodepattern 819, and an ITO glass 820 in the middle. AC signals 702 drivethe electrodes on one axis, and the response through the screen loopsback via the electrodes on the other axis. Location of a pointer 900touching the screen is determined based on the signal level changes 703between the horizontal and vertical electrodes.

Advantages of projective capacitive touch screens are finger mufti-touchdetection and a durable surface.

A disadvantage of projected capacitive touch screens is that as a resultof the overlay, the screens are not fully transparent. Anotherdisadvantage is their high cost. Another disadvantage is a limitedtemperature range for operation. Another disadvantage is a limitedcapture speed, due to the capacitive nature of the touch screens.Another disadvantage is a limited screen size, typically less than 5″.Another disadvantage is that surface capacitive touch screens aresusceptible to RF interference and EM interference. Yet anotherdisadvantage is that the accuracy of touch location determinationdepends on the capacitance.

It will thus be appreciated that conventional touch screens are notideal for general use with small mobile devices and devices with largescreens. It would thus be beneficial to provide touch screens thatovercome the disadvantages of conventional resistive and capacitivetouch screens described above.

SUMMARY OF THE DESCRIPTION

The present invention provides touch screens that overcome the drawbacksof conventional resistive and capacitive touch screens.

Aspects of the present invention relate to various embodiments of touchscreens, including inter alia, (i) touch screens with wide light beams,(ii) touch screens with shift-aligned emitters and receivers, (iii)touch screens with highly refractive lenses, (iv) touch screens with alow bezel, (v) light-based touch screens using long thin light guides,(vi) pressure-sensitive light-based touch screens, and (vii) touchscreens that use a reflected image to calculate a pointer location inthree dimensions. Further aspects of the present invention relate tomethods for touch screens, including inter alia (viii) methods for touchdetection, and (ix) methods for calibrating touch screen components.Still further aspects of the present invention relate to preciseplacement and alignment of elements as required in certain embodimentsof the present invention, as well as in other applications. Such aspectsinclude (x) forming inter-fitting blocks that combine an emitter orreceiver element and a lens, and (xi) methods for guiding an elementduring device assembly using a capillary effect.

Touch Screens with Wide Light Beams

In these embodiments of the present invention light from a narrowsource, such as a near infrared LED, is widened, using lenses orreflective elements, to project over a wide swath of screen area. Inorder to widen a narrow cone of light, the light source is placed at arelatively long distance away from the screen edge. In one embodiment,the light source is placed underneath the screen, at an appropriatedistance from the screen edge to allow for a gradual widening of thebeam. The widened beam is reflected above the screen surface byreflectors placed near the screen edge.

In another embodiment of the present invention the light source isplaced along a screen edge. Reflectors that reflect light over thescreen surface are also placed along the same screen edge, at a suitabledistance away from the light source, to allow for a gradual widening ofthe light beam before it is reflected over the screen surface. The lightsource emits a narrow cone of light substantially along the screen edge,and the light is reflected as a wide beam over the screen surface. Apointer, such as a finger or stylus, touching the screen blocks some ofthe emitted light. By measuring the blocked light, the location of thepointer on the screen is determined.

In an embodiment of the present invention the wide beam converges onto anarrow light detector after traversing the screen, via reflectors placeda suitable distance away from respective light detectors. The lightdetectors are placed either underneath the screen, or along a screenedge.

Touch Screens with Shift-Aligned Emitters and Receivers

In these embodiments of the present invention an arrangement of lightemitters send light over the screen surface to an arrangement of lightreceivers, where the emitters are shift-aligned with the opposingreceivers. As such, instead of light from each emitter being detected byone opposite receiver, light from each emitter arrives at two oppositereceivers. Similarly, instead of each receiver detecting light from oneopposite emitter, each receiver detects light from two oppositeemitters. Such overlapping detection ensures that a touch on the screenis detected by at least two emitter-receiver pairs. In some embodimentsan arrangement of shift-aligned lenses is used to ensure that light fromeach emitter arrives at two opposite receivers, and that each receiverdetects light from two opposite emitters.

There is thus provided in accordance with an embodiment of the presentinvention a touch screen including a housing, a display mounted in thehousing, a row of light pulse emitters, mounted in the housing, thattransmit light pulses over the display, a row of light pulse receivers,mounted in the housing, that receive the light pulses, and a calculatingunit, mounted in the housing and connected to the receivers, thatdetermines a location of a pointer on the display that partially blocksthe light pulses transmitted by the emitters, based on outputs of thereceivers, wherein the emitters are shift-aligned with the receivers.

There is additionally provided in accordance with an embodiment of thepresent invention a touch screen including a housing, a display mountedin the housing, a frame of collimating lenses surrounding the display,wherein the collimating lenses along a first edge of the frame areshift-aligned with the collimating lenses along an opposite edge of theframe, a plurality of light pulse emitters mounted in the housing thattransmit light pulses over the display through the collimating lenses ofthe first edge, a plurality of light pulse receivers mounted in thehousing that receive the light pulses through the collimating lenses ofthe opposite edge, and a calculating unit, mounted in the housing andconnected to the receivers, to determine a location of a pointer on thedisplay that partially blocks the light pulses transmitted by theemitters, based on outputs of the receivers.

There is further provided in accordance with an embodiment of thepresent invention a touch screen including a housing, a display mountedin the housing, a plurality of collimating lenses mounted in the housingand surrounding the display, wherein the collimating lenses along afirst edge of the display are shift-aligned with the collimating lensesalong an opposite edge of the display, a plurality of light pulseemitters mounted in the housing that transmit light pulses over thedisplay through the collimating lenses of the first edge, a plurality oflight pulse receivers mounted in the housing that receive the lightpulses through the collimating lenses of the opposite edge, and acalculating unit, mounted in the housing and connected to the receivers,to determine a location of a pointer on the display that partiallyblocks the light pulses transmitted by the emitters, based on outputs ofthe receivers.

Aspects of the present invention employ a novel collimating lens coupledwith a surface of micro-lenses that refract light to form multiple widedivergent beams. When the surface of micro-lenses is on a surface notfacing an emitter or receiver element, such a collimating lens transmitslight in two stages. As light passes through the body of the lens, lightbeams are collimated, as with conventional collimating lenses. However,as the light passes through the surface of micro-lenses, the light isrefracted into multiple wide divergent beams. When the surface ofmicro-lenses is on a surface facing an emitter or receiver element, sucha collimating lens outputs beams substantially similar to those producedby a collimating lens having an outer surface of micro-lenses.

Touch Screens with Highly Refractive Lenses

In these embodiments of the present invention an arrangement of one ormore light emitters send light over the screen surface to an arrangementof one or more light receivers. The light emitters and the lightreceivers use highly refractive lenses. Light passing through the lenseson the emitter side creates a pattern of highly divergent light beamsthat traverse the screen, thus ensuring that (a) a pointer touching thescreen will block multiple light beams originating along a large sectionof the emitter edge, and (b) at any point along the receiver edge of thescreen, multiple light beams originating along a large section of theemitter edge converge. As such, a touch on the screen is detected byeach of multiple beams along a large section of the receiver edge. Thelenses on the receiver side refract multiple incoming light beams toensure that the beams converging at each point along the receiver edgeare detected by the receivers.

There is thus provided in accordance with an embodiment of the presentinvention a touch screen including a housing, a display mounted in thehousing, a light guide frame surrounding the display, the frameincluding patterns of micro-lenses along two opposing sides of the framefor refracting incoming light in multiple directions, a plurality oflight pulse emitters mounted in the housing that transmit light pulsesover the display through the patterns of micro-lenses along a first edgeof the frame, a plurality of light pulse receivers mounted in thehousing that receive the light pulses through the patterns ofmicro-lenses along the opposite edge of the frame, and a calculatingunit, mounted in the housing and connected to the receivers, todetermine a location of a pointer on the display that partially blocksthe light pulses transmitted by the emitters, based on outputs of thereceivers.

There is additionally provided in accordance with an embodiment of thepresent invention a touch screen including a housing, a display mountedin the housing, two light guides mounted in the housing and arrangedalong two opposite edges of the display, each light guide including apattern of micro-lenses for refracting incoming light in multipledirections, a plurality of light pulse emitters mounted in the housingthat transmit light pulses over the display through a first light guide,a plurality of light pulse receivers mounted in the housing that receivethe light pulses through a second light guide, and a calculating unit,mounted in the housing and connected to the receivers, to determine alocation of a pointer on the display that partially blocks the lightpulses transmitted by the emitters, based on outputs of the receivers.

Further, in accordance with an embodiment of the present invention, thelight emitters and light receivers are positioned below the screensurface, and light is directed above and across the screen surface by afirst light guide positioned along a first screen edge, the light guideincluding a collimating lens for each light emitter, each collimatinglens having a plurality of micro-lenses etched thereon. The collimatinglenses are positioned below the screen surface.

Yet further, in accordance with an embodiment of the present invention,a second light guide is positioned along a second screen edge oppositethe first screen edge, to direct light beams from the first light guideto the light receivers below the screen surface. Moreover, the secondlight guide may be substantially similar to the first light guide,including a lens with a plurality of micro-lenses etched thereon foreach light receiver.

There is additionally provided in accordance with an embodiment of thepresent invention a touch screen system, including a plurality of lightemitters and light receivers that are positioned along respectiveopposite edge of the screen, and not below the screen surface. Light isdirected from the emitters across the screen surface by collimatinglenses that have a plurality of micro-lenses etched thereon, anddirected to the receivers by similar lenses.

Touch Screens with a Low Bezel

In these embodiments of the present invention an arrangement of one ormore light emitters send light over the screen surface to an arrangementof one or more light receivers. Both the light emitters and the lightreceivers are placed below the screen surface. Light from the emittersis reflected over the screen by a reflective light guide that extendsabove the screen. Similarly, light that has passed over the screensurface is reflected onto the receivers by a reflective light guide. Theheight of these reflective light guides above the screen creates a bezelsurrounding the screen. A conventional reflective light guide has asubstantially flat reflective surface inclined at a 45° angle to thescreen surface. Light beams vertical to the screen are re-directed bythe light guide to a plane substantially parallel with the screensurface. However, substantially all of the reflective surface extendsabove the screen surface, forming a bezel around the screen. In order toreduce the bezel height, embodiments of the present invention use alight guide having a parabolic reflective surface and a correspondingrefractive elliptical surface to re-direct the light beams. Theparabolic reflective surface does not extend substantially above thescreen surface, thus reducing the bezel height around the screen.Furthermore, the conventional light guide generally has a second surfacesubstantially vertical to the screen surface through which light beamsenter and exit. The abrupt vertical edge makes the bezel prominent andmay be difficult to clean. The elliptical refractive surface used inembodiments of the present invention is less prominent, and is easier toclean. In some embodiments the elliptical refractive surface is part ofthe screen glass.

There is thus provided in accordance with an embodiment of the presentinvention a touch screen including a housing, a display mounted in thehousing, a plurality of light pulse emitters mounted in the housingbelow the display, a plurality of light pulse receivers mounted in thehousing below the display, a first light guide, mounted in the housingalong a first edge of the display, having a substantially parabolicreflective surface and a substantially elliptical refractive surfacefor, respectively, reflecting and refracting light pulses transmitted bythe emitters over the display, a second light guide, mounted in thehousing along an opposite edge of the display, having a substantiallyelliptical refractive surface and a substantially parabolic reflectivesurface for, respectively, refracting and reflecting light pulsestransmitted over the display to the receivers, and a calculating unit,mounted in the housing and connected to the receivers, to determine alocation of a pointer on the display that partially blocks the lightpulses transmitted by the emitters, based on outputs of the receivers.

There is additionally provided in accordance with an embodiment of thepresent invention a touch screen including a housing, a display mountedin the housing, a plurality of light pulse emitters mounted in thehousing below the display, a plurality of light pulse receivers mountedin the housing below the display, a light guide frame mounted in thehousing and surrounding the display, having a substantially parabolicreflective surface and a substantially elliptical refractive surfacealong each edge for, respectively, reflecting and refracting lightpulses transmitted by the emitters over the display to the receivers,and a calculating unit, mounted in the housing and connected to thereceivers, to determine a location of a pointer on the display thatpartially blocks the light pulses transmitted by the emitters, based onoutputs of the receivers.

There is further provided in accordance with an embodiment of thepresent invention a touch system, including a plurality of lightemitters and light receivers positioned below the screen surface, andlight is directed above and across the screen surface by light guidesthat each have at least two units; namely, a first unit having acollimating lens at one end and a plurality of micro-lenses along asurface at the other end, and a second unit that re-directs light overthe screen surface.

Yet further, the second unit includes at least two active surfaces;namely, a first surface that is a parabolic or a quasi-parabolicreflective surface that folds incoming light beams into a focallocation, and a second surface that is a complementary elliptical orquasi-elliptical surface having the same focal location, wherein thesecond surface directs the folded light beams over the screen surface.

There is moreover provided in accordance with an embodiment of thepresent invention a touch screen system, including a plurality of lightemitters and light receivers positioned below a display screen, and afirst light guide along at least one edge of the screen that reflectslight from the emitters above the screen. The light guide includes atleast two active surfaces; namely, a first surface that is a parabolicor a quasi-parabolic reflective surface that folds incoming light beamsinto a focal location, and a second surface that is a complementaryelliptical or quasi-elliptical surface having the same focal location.The second surface directs the folded light beams over the screensurface.

Additionally, a second light guide is positioned opposite the firstlight guide across the screen, to direct light beams from the firstlight guide to light receivers below the screen. The second light guidemay be substantially similar to the first light guide.

Touch Screens Using Long Thin Light Guides

There is provided in accordance with an embodiment of the presentinvention a touch screen including a housing, a display mounted in thehousing, a plurality of collimating lenses mounted in the housing andarranged along a first edge of the display, a plurality of light pulseemitters mounted in the housing that are spaced apart from and seriallytransmit light pulses through the collimating lenses over the display, alight guide mounted in the housing along the edge of the displayopposite the first edge, for receiving the light pulses, the light guideincluding a reflective strip that reflects light pulses received alongthe length of the light guide to one end of the light guide, a lightpulse receiver mounted in the housing near the one end of the lightguide, for receiving the reflected light pulses, and a calculating unit,mounted in the housing and connected to the receiver, for determining alocation of a pointer on the display that partially blocks light pulsestransmitted by the emitters, based on outputs of the receiver.

There is additionally provided in accordance with an embodiment of thepresent invention a touch screen including a housing, a display mountedin the housing, a light guide mounted in the housing along a first edgeof the display, the light guide including a reflective strip thatreflects light pulses received along the length of the light guide toboth ends of the light guide, a plurality of light pulse receiversmounted in the housing near each end of the light guide, for receivingthe reflected light pulses, a plurality of collimating lenses mounted inthe housing along the edge of the display opposite the first edge, aplurality of light pulse emitters mounted in the housing that are spacedapart from and emit light pulses over the display though the collimatinglenses, and a calculating unit, mounted in the housing and connected tothe receivers, for determining a location of a pointer on the displaythat partially blocks the light pulses transmitted by the emitters,based on outputs of the receivers.

There is further provided in accordance with an embodiment of thepresent invention a touch screen including a housing, a display mountedin the housing, a light guide mounted in the housing along a first edgeof the display, the light guide including a reflective strip thatreflects light pulses received at one end of the light guide, a lightpulse emitter mounted in the housing near the one end of the lightguide, for transmitting light pulses through the light guide, whereinthe reflective strip reflects the light pulses over the display, aplurality of collimating lenses mounted in the housing along the edge ofthe display opposite the first edge, a plurality of light pulsereceivers mounted in the housing that are spaced apart from and receivelight pulses through the collimating lenses, and a calculating unit,mounted in the housing and connected to the receivers, for determining alocation of a pointer on the display that partially blocks the lightpulses transmitted by the emitter, based on outputs of the receivers.

There is yet further provided in accordance with an embodiment of thepresent invention a touch screen including a housing, a display mountedin the housing, a light guide mounted in the housing along a first edgeof the display, the light guide including a reflective strip thatreflects light pulses received at either end of the light guide, aplurality of light pulse emitters mounted in the housing near each endof the light guide, for transmitting light pulses through the lightguide, wherein the reflective strip reflects the light pulses over thedisplay, a plurality of collimating lenses mounted in the housing alongthe edge of the display opposite the first edge, a plurality of lightpulse receivers mounted in the housing that are spaced apart from andreceive light pulses through the collimating lenses, and a calculatingunit, mounted in the housing and connected to the receivers, fordetermining a location of a pointer on the display that partially blocksthe light pulses transmitted by the emitters, based on outputs of thereceivers.

Touch Screens Using a Reflected Image to Determine a Height of a PointerAbove a Touch Screen

There is provided in accordance with an embodiment of the presentinvention a touch screen system including a reflective display surface,a camera mounted so as to capture an image of (i) the reflective displaysurface, (ii) a pointer approaching the reflective display surface, and(iii) a reflection of the pointer on the reflective display surface, anda processor coupled with the camera that determines a three-dimensionallocation of the pointer relative to the reflective display surface,based on the positions of the pointer and the reflection of the pointerin the image captured by the camera.

Pressure-Sensitive Light-Based Touch Screens

There is provided in accordance with an embodiment of the presentinvention a light-based touch screen that discriminates between hardtouches and soft touches. In one embodiment, a rigidly mounted screen issurrounded by emitters and receivers. A hard touch is discriminated froma soft touch by an increase in detected light at a plurality ofreceivers, the increase resulting from a bending of the rigidly mountedscreen caused by the hard touch. In another embodiment, a screen isflexibly mounted in a housing surrounded by rigidly mounted emitters andreceivers. The pressure of the touch lowers the screen into the housing,resulting in an increase in detected light at a plurality of thereceivers. Different amounts of pressure correspond to differences inthe increased amounts of detected light.

Methods for Touch Detection

There is provided in accordance with an embodiment of the presentinvention a method of calculating a touch coordinate on a touch screen,including providing a display, a row of light pulse emitters thattransmit light pulses over the display, and a row of light pulsereceivers that receive the light pulses and that output signalsrepresenting the received light pulses, wherein the emitters areshift-aligned with corresponding receivers, detecting a touch on thedisplay that partially blocks the light pulses, based on the receiveroutputs, selecting a maximum touch detection receiver output,identifying the emitter-receiver pair corresponding to the maximum touchdetection receiver output, selecting at least one emitter-receiver pairto the left, and at least one emitter-receiver pair to the right of themaximum touch detection emitter-receiver pair, for each of the at leastthree emitter-receiver pairs, identifying a respective correspondingtouch screen coordinate, for each of the at least three emitter-receiverpairs, calculating a product of the emitter-receiver pair coordinate andits respective touch detection output signal, calculating a first sum ofthe products, calculating a second sum of the receiver outputs,calculating a spatially-filtered touch coordinate by dividing the firstsum by the second sum, providing a reference touch coordinate based onprevious touch detection signals, calculating a temporally-filteredtouch coordinate based on the spatially-filtered touch coordinate andthe reference touch coordinate, and assigning either (i) thetemporally-filtered touch coordinate value, or (ii) a value thatcombines the temporally-filtered touch coordinate and the referencetouch coordinate, to the reference touch coordinate.

There is additionally provided in accordance with an embodiment of thepresent invention a touch screen system, including a plurality of lightemitters and light receivers, wherein light from each emitter isdetected by more than one receiver, and each receiver detects light frommore than one emitter. Further, a touch location is determined based on(a) signal difference at two receivers that detect light from the sameemitter, and/or (b) signal difference at a receiver that detects lightfrom two emitters. Alternatively, a touch location is determined basedon (a) signal differences at three or more receivers that detect lightfrom the same emitter, and (b) signal differences at a receiver thatdetects light from three or more emitters. Yet further, each emitter issituated opposite a midpoint between two receivers, and each receiver issituated opposite a midpoint between two emitters, with the exception ofemitters and receivers at or near screen corners.

There is additionally provided in accordance with an embodiment of thepresent invention a touch screen system operable to disambiguate amufti-touch operation. Certain mufti-touch operations generate two ormore touch x-coordinates and two or more touch y-coordinates. In suchsituations it is essential to resolve which x-coordinate is associatedwith which y-coordinate. E.g., when two touches performed simultaneouslyare not aligned vertically or horizontally, the two touches generate twotouch x-coordinates and two touch y-coordinates. Similarly, in responseto a rotation gesture, where two fingers touch the screen and glide in acircular pattern around an axis, the screen display, or a screen elementdisplay, is rotated either clockwise or counter-clockwise, according tothe sense of the rotation gesture. As such, it is essential to resolvewhether the sense of the rotation gesture is clockwise orcounter-clockwise. Aspects of the present invention provide a touchscreen system that uses intensities of touch detections to resolvemufti-touch touch locations, and to resolve the sense of a rotationgesture as being clockwise or counter-clockwise.

Methods for Calibrating Touch Screen Components

There is provided in accordance with an embodiment of the presentinvention a method of calibrating optical components in a light-basedtouch screen, including providing a display, a row of light pulseemitters that transmit light pulses over the display according to pulsecurrent and pulse duration controls, and a row of light pulse receiversthat receive the light pulses and that output signals representing thereceived light pulses, determining whether a touch event occurred on thedisplay that partially blocks the light pulses, based on the receiveroutputs, if the determining determines that a touch event has notoccurred, then further determining if the receiver outputs are stable,if the further determining determines that the receiver outputs arestable, then yet further determining if each receiver output is within arespective designated deviation from a respective reference value of thereceiver, if the yet further determining determines that at least onereceiver output is not within its designated deviation from itsreference value, then modifying at least one emitter pulse current andpulse duration, and if the yet further determining determines that allreceiver outputs are within their respective designated deviations fromtheir respective reference values, then assigning the respectivereceiver outputs to their respective reference values.

There is additionally provided in accordance with an embodiment of thepresent invention a method of calibrating optical components in alight-based touch screen, including providing a display, a row of lightpulse emitters that transmit light pulses over the display, and a row oflight pulse receivers that receive the light pulses and that outputsignals representing the received light pulses, determining whether atouch event occurred on the display that partially blocks the lightpulses, based on some of the receiver outputs, if the determiningdetermines that a touch event has occurred, then further determining ifthe remaining receiver outputs are stable, if the further determiningdetermines that the remaining receiver outputs are stable, then yetfurther determining whether the remaining receiver outputs are withinrespective designated deviations from respective reference values of thereceivers, and if the yet further determining determines that theremaining receiver outputs are within their respective designateddeviations from their respective reference values, then assigning therespective remaining receiver outputs to their respective referencevalues.

Inter-Fitting Lens Blocks

There is provided in accordance with an embodiment of the presentinvention a touch screen assembled from pre-fabricated lens blocks. Eachblock is comprised of infra-red transmissive plastic, and is formed as acollimating lens or as a multi-directional collimating lens. Each blockincludes an embedded emitter or receiver that is precisely positionedvis-à-vis the collimating lens. The blocks are formed with curved edgesthat fit into one another, and whereby light from each block enters aneighboring block.

Precision Placement of Elements Using a Capillary Effect

There is provided in accordance with an embodiment of the presentinvention a method of assembling components including inter aliaemitters, receivers and lenses, in a device, wherein a component isplaced into a cavity on the device substrate or guide mold, and a solderpad is placed near the cavity. When the device is inserted into an oven,the solder pad melts and the capillary effect of the molten solder nearthe cavity guides the element deep into the cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood and appreciated fromthe following detailed description, taken in conjunction with thedrawings in which:

FIG. 1 is a prior art illustration of a conventional touch screensystem;

FIG. 2 is a prior art illustration of a conventional resistive touchscreen;

FIG. 3 is a prior art illustration of a conventional surface capacitivetouch screen;

FIG. 4 is a prior art illustration of a conventional projectedcapacitive touch screen;

FIG. 5 is an illustration of a portion of a touch screen including aplurality of emitters that are positioned close together, wherein lightis guided by fiber optic light guides to locations along a first screenedge, in accordance with an embodiment of the present invention;

FIG. 6 is a diagram of a touch screen having 16 emitters and 16receivers, in accordance with an embodiment of the present invention;

FIGS. 7-9 are diagrams of the touch screen of FIG. 6, showing detectionof two pointers that touch the screen simultaneously, in accordance withan embodiment of the present invention;

FIGS. 10 and 11 are diagrams of a touch screen that detects a two fingerglide movement, in accordance with an embodiment of the presentinvention;

FIG. 12 is a circuit diagram of the touch screen from FIG. 6, inaccordance with an embodiment of the present invention;

FIG. 13 is a simplified diagram of a light-based touch screen system, inaccordance with an embodiment of the present invention;

FIG. 14 is a simplified cross-sectional diagram of the touch screensystem of FIG. 13, in accordance with an embodiment of the presentinvention;

FIG. 15 is a simplified illustration of an arrangement of emitters,receivers and optical elements that enable a touch screen system to readpointers that are smaller than the sensor elements, in accordance withan embodiment of the present invention;

FIG. 16 is a simplified illustration of an arrangement of emitters,receivers and optical elements that enable a touch screen system todetect a pointer that is smaller than the sensor elements, includinginter alia a stylus, in accordance with an embodiment of the presentinvention;

FIG. 17 is a simplified diagram of a touch screen with wide light beamscovering the screen, in accordance with an embodiment of the presentinvention;

FIG. 18 is a simplified illustration of a collimating lens, inaccordance with an embodiment of the present invention;

FIG. 19 is a simplified illustration of a collimating lens incooperation with a light receiver, in accordance with an embodiment ofthe present invention;

FIG. 20 is a simplified illustration of a collimating lens having asurface of micro-lenses facing an emitter, in accordance with anembodiment of the present invention;

FIG. 21 is a simplified illustration of a collimating lens having asurface of micro-lenses facing a receiver, in accordance with anembodiment of the present invention;

FIG. 22 is a simplified diagram of an electronic device with a wide-beamtouch screen, in accordance with an embodiment of the present invention;

FIG. 23 is a diagram of the electronic device of FIG. 22, depictingoverlapping light beams from one emitter detected by two receivers, inaccordance with an embodiment of the present invention;

FIG. 24 is a diagram of the electronic device of FIG. 22, depictingoverlapping light beams from two emitters detected by one receiver, inaccordance with an embodiment of the present invention;

FIG. 25 is a diagram of the electronic device of FIG. 22, showing thatpoints on the screen are detected by at least two emitter-receiverpairs, in accordance with an embodiment of the present invention;

FIG. 26 is a simplified diagram of a wide-beam touch screen, showing anintensity distribution of a light signal, in accordance with anembodiment of the present invention;

FIG. 27 is a simplified diagram of a wide-beam touch screen, showingintensity distributions of overlapping light signals from two emitters,in accordance with an embodiment of the present invention;

FIG. 28 is a simplified diagram of a wide-beam touch screen, showingintensity distributions of two sets of overlapping light signals fromone emitter, in accordance with an embodiment of the present invention;

FIG. 29 is a simplified diagram of a wide beam touch screen with emitterand receiver lenses that do not have micro-lens patterns, in accordancewith an embodiment of the present invention;

FIGS. 30 and 31 are simplified diagrams of a wide-beam touch screen withemitter and receiver lenses that have micro-lens patterns, in accordancewith an embodiment of the present invention;

FIG. 32 is a simplified diagram of a wide-beam touch screen with emitterand receiver lenses that do not have micro-lens patterns, in accordancewith an embodiment of the present invention;

FIG. 33 is a simplified diagram of a wide beam touch screen, withemitter and receiver lenses that have micro-lens patterns, in accordancewith an embodiment of the present invention;

FIG. 34 is a simplified diagram of two emitters with lenses that havemicro-lens patterns integrated therein, in accordance with an embodimentof the present invention;

FIG. 35 is a simplified diagram of two receivers with lenses that havemicro-lens patterns integrated therein, in accordance with an embodimentof the present invention;

FIG. 36 is a simplified diagram of a side view of a single-unit lightguide, in the context of an electronic device with a display and anouter casing, in accordance with an embodiment of the present invention;

FIG. 37 is a simplified diagram of side views, from two differentangles, of a lens with applied feather patterns on a surface, inaccordance with an embodiment of the present invention;

FIG. 38 is a simplified diagram of a portion of a wide-beam touchscreen, in accordance with an embodiment of the present invention;

FIG. 39 is a top view of a simplified diagram of light beams enteringand exiting micro-lenses etched on a lens, in accordance with anembodiment of the present invention;

FIG. 40 is a simplified diagram of a side view of a dual-unit lightguide, in the context of a device having a display and an outer casing,in accordance with an embodiment of the present invention;

FIG. 41 is a picture of light guide units, within the content of adevice having a PCB and an outer casing, in accordance with anembodiment of the present invention;

FIG. 42 is a top view of the light guide units of FIG. 41, in accordancewith an embodiment of the present invention;

FIG. 43 is a simplified diagram of a side view cutaway of a light guidewithin an electronic device, in accordance with an embodiment of thepresent invention;

FIG. 44 is a simplified diagram of a side view cutaway of a portion ofan electronic device and an upper portion of a light guide with at leasttwo active surfaces for folding light beams, in accordance with anembodiment of the present invention;

FIG. 45 is a simplified drawing of a section of a transparent opticaltouch light guide, formed as an integral part of a protective glasscovering a display, in accordance with an embodiment of the presentinvention;

FIG. 46 is a simplified illustration of the electronic device and lightguide of FIG. 44, adapted to conceal the edge of the screen, inaccordance with an embodiment of the present invention;

FIG. 47 is a simplified diagram of a light guide that is a single unitextending from opposite an emitter to above a display, in accordancewith an embodiment of the present invention;

FIG. 48 is a simplified diagram of a dual-unit light guide, inaccordance with an embodiment of the present invention;

FIG. 49 is an illustration of optical components made of plasticmaterial that is transparent to infrared light, in accordance with anembodiment of the present invention;

FIG. 50 is a simplified diagram of a side view of a touch screen withlight guides, in accordance with an embodiment of the present invention;

FIG. 51 is an illustration of a touch screen with a block of threeoptical components on each side, in accordance with an embodiment of thepresent invention;

FIG. 52 is a magnified illustration of one of the emitter blocks of FIG.51, in accordance with an embodiment of the present invention;

FIG. 53 is an illustration of a touch screen having a long thin lightguide along a first edge of the screen, for directing light over thescreen, and having an array of light receivers arranged along anopposite edge of the screen for detecting the directed light, and forcommunicating detected light values to a calculating unit, in accordancewith an embodiment of the present invention;

FIG. 54 is an illustration of a touch screen having an array of lightemitters along a first edge of the screen for directing light beams overthe screen, and having a long thin light guide for receiving thedirected light beams and for further directing them to light receiverssituated at both ends of the light guide, in accordance with anembodiment of the present invention;

FIG. 55 is an illustration of two light emitters, each emitter coupledto each end of a long thin light guide, in accordance with an embodimentof the present invention;

FIGS. 56-59 are illustrations of a touch screen that detects occurrenceof a hard press, in accordance with an embodiment of the presentinvention;

FIGS. 60 and 61 are bar charts showing increase in light detected, whenpressure is applied to a rigidly mounted 7-inch LCD screen, inaccordance with an embodiment of the present invention;

FIG. 62 is a simplified diagram of an image sensor positioned beneath ascreen glass display, to capture an image of the underside of the screenglass and touches made thereon, in accordance with an embodiment of thepresent invention;

FIG. 63, which is a simplified diagram of a display divided into pixels,and three touch detections, in accordance with an embodiment of thepresent invention;

FIG. 64 is a simplified diagram of a camera sensor positioned on a hingeof a laptop computer and pointing at a screen, in accordance with anembodiment of the present invention;

FIG. 65 is a simplified side view diagram showing a camera viewing atouch area, in accordance with an embodiment of the present invention;

FIG. 66 is a simplified top view diagram showing a camera viewing atouch area, in accordance with an embodiment of the present invention;

FIG. 67 is a simplified diagram of a camera viewing a touch area, andtwo image axes, an image x-axis and an image y-axis, for locating atouch pointer based on an image captured by the camera, in accordancewith an embodiment of the present invention;

FIG. 68 is a simplified diagram of a camera viewing a touch area, andtwo screen axes, a screen x-axis and a screen y-axis, for locating atouch pointed based on an image captured by the camera, in accordancewith an embodiment of the present invention;

FIGS. 69 and 70 are simplified diagrams of two cameras, each capturing atouch area from different angles, in accordance with an embodiment ofthe present invention;

FIG. 71 is a simplified diagram of four cameras, each capturing a toucharea from different angles, in accordance with an embodiment of thepresent invention;

FIG. 72 is a simplified diagram, from a camera viewpoint, of a cameraviewing a complete touch area, in accordance with an embodiment of thepresent invention;

FIG. 73 is a simplified diagram of a portion of a touch area showing astylus and a mirror image of the stylus, which are tangent to oneanother, in accordance with an embodiment of the present invention;

FIG. 74 is a simplified diagram showing a stylus and a mirror image ofthe stylus, moved closer to the center of a touch area vis-à-vis FIG.73, in accordance with an embodiment of the present invention;

FIG. 75 is a simplified diagram showing a stylus and a mirror image ofthe stylus, moved closer to the bottom of a touch area vis-à-vis FIG.73, in accordance with an embodiment of the present invention;

FIG. 76 is a simplified diagram showing a stylus and a mirror image ofthe stylus, separated apart from one another, in accordance with anembodiment of the present invention;

FIG. 77 is a simplified flowchart of a method for determining athree-dimensional pointed location, in accordance with an embodiment ofthe present invention;

FIG. 78 is a simplified diagram of a touch area that displays six touchicons, used for determining a camera orientation, in accordance with anembodiment of the present invention;

FIGS. 79 and 80 are illustrations of opposing rows of emitter andreceiver lenses in a touch screen system, in accordance with anembodiment of the present invention;

FIG. 81 is a simplified illustration of a technique for determining atouch location, by a plurality of emitter-receiver pairs in a touchscreen system, in accordance with an embodiment of the presentinvention;

FIG. 82 is an illustration of a light guide frame for the configurationof FIGS. 79 and 80, in accordance with an embodiment of the presentinvention;

FIG. 83 is a simplified flowchart of a method for touch detection for anoptical touch screen, in accordance with an embodiment of the presentinvention;

FIGS. 84-86 are illustrations of a rotation gesture, whereby a userplaces two fingers on the screen and rotates them around an axis;

FIGS. 87-90 are illustrations of touch events at various locations on atouch screen, in accordance with an embodiment of the present invention;

FIGS. 91-94 are respective bar charts of light saturation during thetouch events illustrated in FIGS. 87-90, in accordance with anembodiment of the present invention;

FIG. 95 is a simplified flowchart of a method for determining thelocations of simultaneous, diagonally opposed touches, in accordancewith an embodiment of the present invention;

FIG. 96 is a simplified flowchart of a method for discriminating betweenclockwise and counter-clockwise gestures, in accordance with anembodiment of the present invention;

FIG. 97 is a simplified flowchart of a method of calibration and touchdetection for an optical touch screen, in accordance with an embodimentof the present invention;

FIG. 98 is a picture showing the difference between signals generated bya touch, and signals generated by a mechanical effect, in accordancewith an embodiment of the present invention;

FIG. 99 is a simplified diagram of a control circuit for setting pulsestrength when calibrating an optical touch screen, in accordance with anembodiment of the present invention;

FIG. 100 is a plot of calibration pulses for pulse strengths rangingfrom a minimum current to a maximum current, for calibrating an opticaltouch screen in accordance with an embodiment of the present invention;

FIG. 101 is a simplified pulse diagram and a corresponding output signalgraph, for calibrating an optical touch screen, in accordance with anembodiment of the present invention;

FIG. 102 is an illustration showing how a capillary effect is used toincrease accuracy of positioning a component, such as an emitter or areceiver, on a printed circuit board, in accordance with an embodimentof the present invention; and

FIG. 103 is an illustration showing the printed circuit board of FIG.102, after having passed through a heat oven, in accordance with anembodiment of the present invention.

For reference to the figures, the following index of elements and theirnumerals is provided. Elements numbered in the 100's generally relate tolight beams, elements numbered in the 200's generally relate to lightsources, elements numbered in the 300's generally relate to lightreceivers, elements numbered in the 400's and 500's generally relate tolight guides, elements numbered in the 600's generally relate todisplays, elements numbered in the 700's generally relate to circuitelements, elements numbered in the 800's generally relate to electronicdevices, and elements numbered in the 900's generally relate to userinterfaces. Elements numbered in the 1000's are operations of flowcharts.

Similarly numbered elements represent elements of the same type, butthey need not be identical elements.

Elements generally related to light beams Element Description 100-102Generic light beams 105, 106 Reflected light beam 142 Arc of lightoutput from light source 143 Arc of light input to light receiver 144Wide light beams 145-148 Edge of wide light beam 151-154 Light beams 158Wide light beam 167-169 Wide light beam 170-172 Signals received bylight receivers 173 Beam from 1 emitter to 2 receivers 174 Beam from 1emitter to 1^(st) receiver 175 Beam from 1 emitter to 2^(nd) receiver176 Beam from emitter to 1^(st) receiver 177 Beam from emitter to 2^(nd)receiver 178 Beam from 1 emitter to 1^(st) receiver 179 Beam from 1emitter to 2^(nd) receiver 182 Beam from 1 emitter to 2 receivers183-188 Middle of arc of light 190 Light beams output from light source191 Light beams input to light receiver 192 Arcs of light

Elements generally related to light sources Element Description 200-203Generic light emitters 235-241 Light emitters

Elements generally related to light receivers Element Description300-305 Generic light receivers 394 Light receiver 398 Lightreceiver/light emitter

Elements generally related to light guides Element Description 400Generic lens 401, 402 Fiber optic light guides 407 Raised reflectorbezel 408 Cutout 437, 438 Reflector & lens 439-443 Lens 444 Micro-lenses445 Surface with fan of micro-lenses 450 Light guide 451, 452 Internallyreflective surface 453, 454 Light guide surface 455 Light guide 456Internally reflective surface 457 Collimating lens & reflective surface458 Micro-lenses 459 Light guide surface 460 Surface with fan ofmicro-lenses 461 Lens 462 Micro-lenses 463 Upper portion of light guide464 Lower portion of light guide 465 Light guide surface 466 Surfacewith parallel row micro-lenses 467 Parallel row pattern of micro-lenses468 Light guide 469, 470 Internally reflective surface 471 Light guidesurface 472 Light guide 473 Internally reflective surface 474 Lightguide surface 475 Focal line of a lens 476 Light guide 477 Internallyreflective surface 478 Light guide surface 479 Light guide 480Internally reflective surface 481 Light guide surface 482 Black plastictransmissive element 483 Light guide 484 Surface with fan ofmicro-lenses 485 Upper portion of light guide 486 Lower portion of lightguide 487 Surface with parallel row micro-lenses 488, 489 Opticalcomponent 490-492 Surface of optical component 493 Lens 494-497 Opticalcomponent 498, 499 Light guide 500-501 Emitter optical component block502-503 Receiver optical component block 504 Emitter lenses 505 Receiverlenses 506, 507 Emitter optical component 508-510 Receiver opticalcomponent 511 Emitter optical component 512 Receiver optical components513 Optical component/temporary guide 514 Long thin light guide 515Light guide reflector 516 Micro-lenses 517 Light scatterer strip 518,519 Light guides 520, 521 Protruding lips on light guides 522, 523Relative position of light guide element 524 Clear, flat glass 525Collimating lens 526 Clear flat glass with micro-lens surface 527Collimating lens with micro-lens surface

Elements generally related to displays Element Description 600 Genericscreen glass 606 LCD display (prior art) 607 Screen glass (prior art)635-637 Display 638 Protective glass 639 Daylight filter sheet 640Protective glass 641 Daylight filter sheet 642, 643 Display 645Reflection on display glass

Elements generally related to circuit elements Element Description 700Generic printed circuit board 701 Controller integrated circuit (pr.art) 702 AC input signal (prior art) 703 Output signal (prior art) 720Shift register for column activation 730 Shift register for columnactivation 760, 761 Electrical pad 762, 763 Printed circuit board 764Guide pin 765 Solder pad 766 Component solder pad 767 Solder pads afterheat oven 768, 769 Notch in optical component/guide 770 Calculating unit771 Clip-on fastener

Elements generally related to touch-based electronic devices ElementDescription 800 Generic touch screen 801 Touch overlay (prior art) 802Conductive & resistive layers (pr. art) 803 PET film (prior art) 804 Topcircuit layer (prior art) 805 Bottom circuit layer (prior art) 806, 807Conductive coating (prior art) 808 Spacer dot (prior art) 809 Touchsurface (prior art) 810 Coated glass substrate (prior art) 811 Glasssubstrate (prior art) 812 Conductive ITO coating (prior art) 813 Silicondioxide hard coating (prior art) 814 Electrode (prior art) 815 EtchedITO layers (prior art) 816, 817 Hard coat layer (prior art) 818 x-axiselectrode pattern (prior art) 819 y-axis electrode pattern (prior art)820 ITO glass (prior art) 826 Electronic device 827-833 Device casing841, 842 Resilient members 843 Flex air gap 844-847 Image sensors 848Laptop computer

Elements generally related to user interfaces Element Description900-903 Pointer/finger/thumb/stylus 905-908 Detected touch area 965-970Touch icons 971, 972 Touch points 973-976 Light signal attenuation area977 Point on lens 980 Touch point 981, 982 Point on lens 989, 990 Pin991-993 Active touch area 996-999 Mid-line between pointer andreflection

DETAILED DESCRIPTION

Aspects of the present invention relate to light-based touch screens andlight-based touch surfaces.

For clarity of exposition, throughout the present specification the term“touch screen” is used as a generic term to refer to touch sensitivesurfaces that may or may not include an electronic display. As such, theterm “touch screen” as used herein includes inter alia a mouse touchpadas included in many laptop computers, and the cover of a handheldelectronic device. The term “optical touch screen” is used as a genericterm to refer to light-based touch screens, including inter alia screensthat detect a touch based on the difference between an expected lightintensity and a detected light intensity, where the detected lightintensity may be greater than or less than the expected light intensity.The term “screen glass” is used as a generic term to refer to atransparent screen surface. The screen may be constructed inter aliafrom glass, or from a non-glass material including inter alia crystal,acrylic and plastic. In some embodiments of the present invention, thescreen allows near-infrared light to pass through, but is otherwisenon-transparent.

For clarity of exposition, throughout the present specification, theterm “emitter” is used as a generic term to refer to a light emittingelement, including inter alia a light-emitting diode (LED), and theoutput end of a fiber optic or tubular light guide that outputs lightinto a lens or reflector that directs the light over a display surface.The term “receiver” is used as a generic term to refer to a lightdetecting element, including inter alia a photo diode (PD), and theinput end of a fiber optic or tubular light guide that receives lightbeams that traversed a display surface and directs them to a lightdetecting element or to an image sensor, the image sensor being interalia a charge coupled device (CCD) or a complementary metal oxidesemiconductor (CMOS) image sensor.

Reference is made to FIG. 5, which is an illustration of a portion of atouch screen including a plurality of emitters 201-203 that arepositioned close together, wherein light is guided by fiber optic lightguides 401 to locations along a first screen edge, in accordance with anembodiment of the present invention. The portion of the touch screenalso includes a plurality of receivers 301-305 that are positioned closetogether, wherein light is guided thereto by fiber optic light guides402 from locations a long a second screen edge.

According to embodiments of the present invention, a light-based touchscreen includes one or more emitters, including inter alia infra-red ornear infra-red light-emitting diodes (LEDs), and a plurality ofreceivers, including inter alia photo diodes (PDs), arranged along theperimeter surrounding the touch screen or touch surface. The emittersproject light substantially parallel to the screen surface, and thislight is detected by the receivers. A pointer, such as a finger or astylus, placed over a portion of the screen blocks some of the lightbeams, and correspondingly some of the receivers detect less lightintensity. The geometry of the locations of the receivers, and the lightintensities they detect, suffice to determine screen coordinates of thepointer. The emitters and receivers are controlled for selectiveactivation and de-activation by a controller. Generally, each emitterand receiver has I/O connectors, and signals are transmitted to specifywhich emitters and which receivers are activated.

In an embodiment of the present invention, plural emitters are arrangedalong two adjacent sides of a rectangular screen, and plural receiversare arranged along the other two adjacent sides. In this regard,reference is now made to FIG. 6, which is a diagram of a touch screen800 having 16 emitters 200 and 16 receivers 300, in accordance with anembodiment of the present invention. Emitters 200 emit infra-red or nearinfra-red light beams across the top of the touch screen, which aredetected by corresponding receivers 300 that are directly oppositerespective emitters 200. When a pointer touches touch screen 800, itblocks light from reaching some of receivers 300. By identifying, fromthe receiver outputs, which light beams have been blocked by thepointer, the pointer's location can be determined.

Reference is now made to FIGS. 7-9, which are diagrams of touch screen800 of FIG. 6, showing detection of two pointers, 901 and 902, thattouch the screen simultaneously, in accordance with an embodiment of thepresent invention. When two or more pointers touch the screensimultaneously, this is referred to as a “multi-touch.” Pointers 901 and902, which are touching the screen, block light from reaching some ofreceivers 300. In accordance with an embodiment of the presentinvention, the locations of pointers 901 and 902 are determined from thecrossed lines of the infra-red beams that the pointers block. Indistinction, prior art resistance-based and capacitance-based touchscreens are generally unable to detect a multi-touch.

When two or more pointers touch screen 800 simultaneously along a commonhorizontal or vertical axis, the positions of the pointers aredetermined by the receivers 300 that are blocked. Pointers 901 and 902in FIG. 7 are aligned along a common vertical axis and blocksubstantially the same receivers 300 along the bottom edge of touchscreen 800; namely the receivers marked a, b, c and d. Along the leftedge of touch screen 800, two different sets of receivers 300 areblocked. Pointer 901 blocks the receivers marked e and f, and pointer902 blocks the receivers marked g and h. The two pointers are thusdetermined to be situated at two locations. Pointer 901 has screencoordinates located at the intersection of the light beams blocked fromreceivers a-d and receivers e and f; and pointer 902 has screencoordinates located at the intersection of the light beams blocked fromreceivers a-d and receivers g and h.

Pointers 901 and 902 shown in FIGS. 8 and 9 are not aligned along acommon horizontal or vertical axis, and they have different horizontallocations and different vertical locations. From the blocked receiversa-h, it is determined that pointers 901 and 902 are diagonally oppositeone another. They are either respectively touching the top right andbottom left of touch screen 800, as illustrated in FIG. 8; or elserespectively touching the bottom right and top left of touch screen 800,as illustrated in FIG. 9.

Discriminating between FIG. 8 and FIG. 9 is resolved by either (i)associating the same meaning to both touch patterns, or (ii) byassociating meaning to only one of the two touch patterns, or (iii) bymeasuring the amount of light detected at the blocked receivers. In case(i), the UI arranges its icons, or is otherwise configured, such thatthe effects of both touch patterns FIG. 8 and FIG. 9 are the same. Forexample, touching any two diagonally opposite corners of touch screen800 operates to unlock the screen.

In case (ii), the UI arranges its icons, or is otherwise configured,such that only one of the touch patterns FIG. 8 and FIG. 9 has a meaningassociated therewith. For example, touching the upper right and lowerleft corners of touch screen 800 operates to unlock the screen, andtouch the lower right and upper left of touch screen 800 has no meaningassociated therewith. In this case, the UI discriminates that FIG. 8 isthe correct touch pattern.

In case (iii), a finger closer to a receiver blocks more light fromreaching the receiver than does a finger that is farther from thereceiver. In part, this is due to the closer finger blocking moreambient light from reaching the receiver than does the farther finger.The light intensities detected at receivers e and f are compared withthe light intensities detected at receivers g and h. Similarly, thelight intensities detected at receivers a and b are compared with thelight intensities detected at receivers c and d. If the light detectedat receivers e and f and at receivers c and d is greater than the lightdetected at receivers g and h and at receivers a and b, then it isinferred that the fingers are positioned as shown in FIG. 8. Similarly,if the light detected at receivers e and f and at receivers c and d isless than the light detected at receivers g and h and at receivers a andb, then it is inferred that the fingers are positioned as shown in FIG.9. The comparison may be based on summing or averaging the respectiveblocked receivers along each edge separately, e+f vs. g+h, and a+b vs.c+d. Alternatively, the comparison may be based on summing or averagingblocked receivers along two edges; i.e., based on the maximum andminimum of the values a+b+e+f, a+b+g+h, c+d+e+f, and c+d+g+h. Themaximum and minimum values determine the locations of the fingers. E.g.,if c+d+e+f is the maximum value and if a+b+g+h is the minimum value,then it is inferred that the fingers are positioned as shown in FIG. 8.

The number of receivers in each sum depends on the sequence of blocked,or at least partially blocked, receivers. The number of receivers may bedifferent for each sequence. E.g., a sum of four receivers may becompared to a sum of six receivers. In one embodiment of the presentinvention the minimum receiver value in each sequence is used. Theminimum receiver value corresponds to the receiver that is most blockedwithin a sequence of blocked receivers, and is a good indicator ofproximity of the blocking finger to the sequence of receivers.

Determining locations of a diagonally oriented mufti-touch is discussedfurther hereinbelow with reference to shift-aligned arrangements ofemitters and receivers.

Reference is now made to FIGS. 10 and 11, which are diagrams of a touchscreen 800 that detects a two finger glide movement, in accordance withan embodiment of the present invention. The glide movement illustratedin FIGS. 10 and 11 is a diagonal glide that brings pointers 901 and 902closer together. The direction of the glide is determined from changesin which receivers 300 are blocked. As shown in FIGS. 10 and 11, blockedreceivers are changing from a and b to receivers 300 more to the right,and from c and d to receivers 300 more to the left. Similarly, blockedreceivers are changing from e and f to receivers 300 more to the bottom,and from g and h to receivers 300 more to the top. For a glide in theopposite direction, that moves pointers 901 and 902 farther apart, theblocked receivers change in the opposite directions.

When pointers 901 and 902 are aligned in a common vertical or horizontalaxis, there is no ambiguity in identifying glide patterns. When pointers901 and 902 are not aligned in a common vertical or horizontal axis,there may be ambiguity in identifying glide patterns, as illustrated inFIGS. 10 and 11. In case of such ambiguity, and as described hereinabovewith reference to FIGS. 8 and 9, discriminating between FIG. 10 and FIG.11 is resolved by either (i) by associating the same meaning to bothglide patterns, or (ii) by associating meaning to only one of the twoglide patterns, or (iii) by measuring and comparing the amounts of lightdetected at the blocked receivers.

Associating the same meaning to both glide patterns may be performed ina pinch zoom gesture, whereby a user places two fingers on the screenand spreads the fingers apart along a diagonal of the screen. Such agesture activates a zoom-in operation, for increasing the magnificationof graphics displayed on the screen. Such a gesture has the same meaningirrespective of whether the pinch zoom is performed along a top-left tobottom-right diagonal, or along a top-right to bottom-left diagonal.

Similar considerations apply to a zoom-out gesture, whereby a userplaces two fingers on the screen and brings the fingers closer togetheralong a diagonal of the screen, for decreasing the magnification ofgraphics displayed on the screen. This gesture, too, has the samemeaning irrespective of along which diagonal of the screen the gestureis performed.

Reference is made to FIG. 12, which is a circuit diagram of touch screen800 from FIG. 6, in accordance with an embodiment of the presentinvention. The emitters and receivers are controlled by a controller(not shown). The emitters receive respective signals LED00-LED15 fromswitches A, and receive current from VROW and VCOL through currentlimiters B. The receivers receive respective signals PD00-PD15 fromshift register 730. Receiver output is sent to the controller viasignals PDROW and PDCOL. Operation of the controller, of switches A andof current limiters B is described in applicant's co-pendingapplication, U.S. application Ser. No. 12/371,609 filed on Feb. 15, 2009and entitled LIGHT-BASED TOUCH SCREEN, the contents of which are herebyincorporated by reference.

According to an embodiment of the present invention, the emitters arecontrolled via a first serial interface, which transmits a binary stringto a shift register 720. Each bit of the binary string corresponds toone of the emitters, and indicates whether to activate or deactivate thecorresponding emitter, where a bit value “1” indicates activation and abit value “0” indicates deactivation. Successive emitters are activatedand deactivated by shifting the bit string within shift register 720.

Similarly, the receivers are controlled by a second serial interface,which transmits a binary string to a shift register 730. Successivereceivers are activated and deactivated by shifting the bit string inshift register 730. Operation of shift registers 720 and 730 isdescribed in applicant's co-pending application, U.S. application Ser.No. 12/371,609 filed on Feb. 15, 2009 and entitled LIGHT-BASED TOUCHSCREEN, the contents of which are hereby incorporated by reference.

Reference is made to FIG. 13, which is a simplified diagram of alight-based touch screen system, in accordance with an embodiment of thepresent invention. The touch screen of FIG. 13 does not require anoverlay. Instead, a small frame 407 surrounds the display with emitters200 and receivers positioned on opposite sides of the screen, and hiddenbehind an infrared transparent bezel. When a pointer, such as a fingeror a stylus, touches the screen in a specific area 905, one or morelight beams generated by emitters 200 are obstructed. The obstructedlight beams are detected by corresponding decreases in light received byone or more of the receivers, which is used to determine the location ofthe pointer.

Reference is made to FIG. 14, which is a simplified cross-sectionaldiagram of the touch screen system of FIG. 13, in accordance with anembodiment of the present invention. Shown in FIG. 14 is across-sectional view of a section A-A of an LCD display 600 and itssurrounding infrared transparent frame 407. The cross-sectional viewshows an emitter 200 emitting light 100 that is reflected by a cut-out408 in frame 407, and directed substantially parallel over the displaysurface. As a finger 900 approaches near the display surface, some ofthe light, 101, emitted by the emitters and directed over the locationof the near touch is blocked by the finger, and some of the light, 102,passes between the fingertip and the screen glass. When finger 900touches the display surface, all of the light emitted by the emittersand directed over the touch location is blocked by finger 900.

Touch Screen System Configuration No. 1

Reference is made to FIG. 15, which is a simplified illustration of anarrangement of emitters, receivers and optical elements that enable atouch screen system to read pointers that are smaller than the sensorelements, in accordance with an embodiment of the present invention.Shown in FIG. 15 are a mirror or optical lens 400, an emitter 200, awide reflected light beam 105, a pointer 900 and a receiver 300. Mirroror optical lens 400 generates a wide light beam that is focused ontoreceiver 300 by a second mirror or optical lens. The wide beam makes itpossible to sense an analog change in the amount of light detected atreceiver 300 when a pointer blocks a portion of the wide beam. The widebeam enables sensing an analog change when pointer 900 is placed infront of mirror or lens 400. Thus, pointer 900 in FIG. 15 blocks only aportion of wide beam 105. The wide beam also enables mounting theemitters far apart from one another, and mounting the receivers farapart from one another. Consequently, this reduces the bill of materialsby requiring fewer emitters and fewer receivers.

Reference is made to FIG. 16, which is a simplified illustration of anarrangement of emitters, receivers and optical elements that enable atouch screen system to detect a pointer that is smaller than the sensorelements, including inter alia a stylus, in accordance with anembodiment of the present invention. Shown in FIG. 16 are a mirror oroptical lens 400, an emitter 200, a wide reflected light beam, 105, apointer 900 and a receiver 300. Mirror or optical lens 400 generates awide light beam that is focused onto receive 300 by a second mirror oroptical lens. The wide beam enables sensing of an analog change in theamount of light detected at receiver 300 when a pointer 900 blocks aportion of the wide beam, in particular, when pointer 900 is placed infront of mirror or lens 400. Pointer 900, as shown in FIG. 16, blocksonly a portion of wide beam 105, indicated by beam 106 being blocked bythe tip of pointer 900. The wide beam also enables mounting emitters farapart from one another, and mounting receivers far apart from oneanother. In turn, this reduces the bill of materials by requiring feweremitters and fewer receivers.

Without the wide beam, there are generally spaces between beams that goundetected, making it impossible to distinguish between a user dragginga fine-point stylus across the beams, and the user tapping on differentbeams with a fine-point stylus. Moreover, with widely spaced narrowbeams the pointer touch must be very precise in order to cross a narrowbeam.

Reference is made to FIG. 17, which is a simplified diagram of a touchscreen with wide light beams covering the screen, in accordance with anembodiment of the present invention. Touch screen systems using widebeams are described in applicant's provisional patent application, U.S.Application Ser. No. 61/317,255 filed on Mar. 24, 2010 and entitledOPTICAL TOUCH SCREEN WITH WIDE BEAM TRANSMITTERS AND RECEIVERS, thecontents of which are hereby incorporated by reference.

The emitters and receivers shown in FIG. 17 are spaced relatively widelyapart. Generally, the emitters are not activated simultaneously.Instead, they are activated one after another, and the coverage areas oftheir light beams are substantially connected.

FIG. 17 shows a top view and a side view of a touch system having atouch screen or touch surface 800. The touch system providestouch-sensitive functionality to a surface irrespective of whether ornot the surface includes a display screen. Moreover, a physical surfaceis not required; the light beams may be projected though the air, andthe location of a pointer in mid-air that breaks the light beams may bedetected.

Also shown in FIG. 17 are emitters 200, reflectors 437 and 438, andreceivers 300 coupled with a calculating unit 770. Emitters 200 andreceivers 300 are positioned beneath screen 800. Emitters 200 projectarcs 142 of light under screen 800 onto reflectors 437. The distancebetween emitters 200 and reflectors 437 is sufficient for an arc tospread into a wide beam at a reflector 437. In various embodiments ofthe present invention, the distance between emitters 200 and reflectors437 may be approximately 4 mm, 10 mm, 20 mm or greater, depending onfactors including inter alia screen size, required touch resolution,emitter characteristics and optical reflector characteristics.

Reflectors 437 collimate the light as wide beams 144 across a swath ofscreen surface. A wide beam 144 reaches a reflector 438, which (i)redirects the light beam below screen 800, and (ii) narrows the widebeam 144 into an arc 143. As such, wide beam 144 converges onto thesurface of one of receivers 300 below the surface of screen 800. Thelight intensity detected by each of receivers 300 is communicated tocalculating unit 770.

The configuration of FIG. 17 is of advantage in that the wide lightbeams cover the entire screen surface, thereby enabling touch sensitivefunctionality anywhere on the screen. Additionally, the cost ofmaterials for the touch screen is reduced, since relatively few emitterand receiver components are required.

Touch Screen System Configuration No. 2

Configurations 2-5 use multiple emitter-receiver pairs to preciselyidentify a touch position. In some of the configurations describedhereinabove there are opposing rows of emitters and receivers, eachemitter being opposite a respective receiver. In configurations 2-5 theemitters are shift-aligned with the receivers. For example, each emittermay be positioned opposite a midpoint between two opposing receivers.Alternatively, each emitter may be off-axis aligned with an oppositereceiver, but not opposite the midpoint between two receivers.

Embodiments of the present invention employ two types of collimatinglenses; namely, (i) conventional collimating lenses, and (ii)collimating lenses coupled with a surface of micro-lenses that refractlight to form multiple wide divergent beams. As used throughout thepresent specification, the term “collimating lens” includes both typesof lenses. When a light source is positioned at the focus of aconventional collimating lens, the lens outputs light in substantiallyparallel beams, as illustrated inter alia in FIGS. 15-17. When a lightsource is positioned between a conventional collimating lens and itsfocus, the lens outputs a wide beam, the outer edges of which are notparallel to each other, as illustrated inter alia in FIGS. 23-26.

Reference is made to FIG. 18, which is a simplified illustration of acollimating lens in cooperation with a light emitter, in accordance withan embodiment of the present invention. Shown in FIG. 18 is (A) a lightemitter 200 transmitting light beams 190 through a flat clear glass 524.Beams 190 are unaltered by the glass.

Also shown in FIG. 18 is (B) an emitter positioned at the focus of acollimating lens 525. Beams 190 are collimated by lens 525.

Also shown in FIG. 18 is (C) an emitter 200 positioned betweencollimating lens 525 and the lens' focus. Beams 190 are partiallycollimated by lens 525; i.e., the output wide beams are not completelyparallel.

Reference is made to FIG. 19, which is a simplified illustration of acollimating lens in cooperation with a light receiver, in accordancewith an embodiment of the present invention. Shown in FIG. 19 is (A)substantially parallel light beams 191 transmitted through a flat clearglass 524. Beams 191 are unaltered by the glass.

Also shown in FIG. 19 is (B) a receiver 300 positioned at the focus ofcollimating lens 525. Beams 191 are refracted onto receiver 300 bycollimating lens 525.

Also shown in FIG. 19 is (C) a receiver 300 positioned betweencollimating lens 525 and the lens' focus. Beams 191 are collimated bylens 525, but because receiver 300 is not at the lens focus, the beamsdo not converge thereon.

Collimating lenses coupled with an outer surface of micro-lenses, whichface away from emitters or receivers, transmit light in two stages. Aslight passes through the bodies of the lenses, light beams arecollimated as with conventional collimating lenses. However, as thelight passes through the surface of micro-lenses, the light is refractedinto multiple wide divergent beams, as illustrated inter alia in FIGS.30, 31 and 33-35. In FIGS. 34 and 35, collimating lenses 439 and 440 areshown having micro-lens surfaces 444. In FIG. 34, light emitters 201 and202 are positioned within the focal distance of collimating lenses 439and 440, and wide light beams from the emitters are shown enteringlenses 439 and 440. Light is collimated as it passes through the lens,as with conventional collimating lenses. When the collimated lightpasses through micro-lens surface 444, it is refracted into multiplewide divergent beams, three of which are illustrated in FIG. 30. In FIG.35, light receivers 301 and 302 are positioned within the focal distanceof the collimating lenses, and light beams are shown entering lenses 439and 440 through micro-lens surface 444. The incoming beams are refractedinto wide divergent beams inside the lens bodies. The refracted beamsare directed by the collimating portions of lenses 439 and 440, whichconcentrate the beams onto light receivers 301 and 302.

Reference is made to FIG. 20, which is a simplified illustration of acollimating lens having a surface of micro-lenses facing an emitter, inaccordance with an embodiment of the present invention. FIG. 20 shows(A) a flat glass 526 having micro-lenses etched on a surface facing anemitter 200. Light beams 190 enter glass 526 at various angles. At eachentry point, a micro-lens refracts an incoming beam into a wide arc 192.Lines 183 show how the middle of each arc is oriented in a differentdirection, depending on the angle of approach of the beam into glass526.

FIG. 20 also shows (B) a collimating lens 527 having micro-lenses etchedon a surface facing an emitter 200. A focus point of the lens, withoutthe micro-lenses, is determined, and emitter 200 is positioned at thatpoint. Light beams 190 enter collimating lens 527 at various angles. Ateach entry point, a micro-lens refracts the incoming beams into a widearc 192. Lines 184 show how the middle of each arc is oriented in thesame direction, irrespective of the angle of approach of the beams intocollimating lens 527. This type of lens is referred to as a“mufti-directional collimating lens”, because it outputs arcs of light,not parallel beams, but all of the arcs are substantially uniformlydirected.

FIG. 20 also shows (C) the same collimating lens 527, but with emitter200 positioned between the lens and the focus point. The output arcs 192are oriented in directions between those of the arcs of (A) and the arcsof (B), indicated by lines 185.

Reference is made to FIG. 21, which is a simplified illustration of acollimating lens having a surface of micro-lenses facing a receiver, inaccordance with an embodiment of the present invention. FIG. 21 shows(A) a flat glass 526 having micro-lenses etched on a surface facing areceiver 300. Light beams 191 are shown entering glass 526 as parallelbeams. At each exit point, a micro-lens refracts a beam into a wide arc192. Lines 186 show how the middle of each arc is oriented in the samedirection. The arcs do not converge on receiver 300.

FIG. 21 also shows (B) a mufti-directional collimating lens 527 havingmicro-lenses etched on a surface facing receiver 300. A focus point ofthe lens, without the micro-lenses, is determined, and receiver 300 ispositioned at that point. Light beams 191 enter lens 527 assubstantially parallel beams. At each exit point, a micro-lens refractsan incoming beam into a wide arc 192. Lines 187 show how the middle ofeach arc is oriented towards receiver 300.

FIG. 21 also shows (C) the same lens 527, but with receiver 300positioned between the lens and the focus point. The output arcs areoriented in directions between those of the arcs of (A) and the arcs of(B).

As used through the present specification, the term “collimating lens”includes a mufti-directional collimating lens.

Reference is made to FIG. 22, which is a simplified diagram of anelectronic device with a wide-beam touch screen, in accordance with anembodiment of the present invention. Shown in FIG. 22 is an electronicdevice 826 with two emitters, 201 and 202, and three receivers, 301, 302and 303, the emitters and receivers being placed along opposite edges ofa display 636. Light intensities detected at each of receivers 301, 302and 303, are communicated to a calculating unit 770. Each emitter andreceiver uses a respective primary lens, labeled respectively 441, 442,443, 439 and 440. Emitters and receivers use the same lens arrangement,to ensure that light emitted by an emitter and re-directed by an emitterlens, is reverse-directed by an opposing lens onto a receiver.

It is desirable that the light beam from each emitter covers its twoopposite receiver lenses. Such a condition is achieved by positioningeach emitter between its lens and its lens' focal point. As such, theemitter is not in focus and, as a result, its light is spread, insteadof being collimated, by its lens. Each receiver is similarly positionedbetween its lens and its lens' focal point.

Reference is made to FIG. 23, which is a diagram of electronic device826 of FIG. 22, depicting overlapping light beams from one emitterdetected by two receivers, in accordance with an embodiment of thepresent invention. Shown in FIG. 23 are two wide light beams fromemitter 201, one of which is detected at receiver 301 and another ofwhich is detected at receiver 302, respectively. The left and rightsides of the one beam are marked 145 and 146, respectively, and the leftand right sides of the other beam are marked 147 and 148, respectively.The shaded area in FIG. 23 indicates the area on display 636 at which atouch blocks a portion of both wide beams. As such, a touch in this areais detected by two emitter-receiver pairs; namely, 201-301 and 201-302.

Reference is made to FIG. 24, which is a diagram of electronic device826 of FIG. 22, depicting overlapping light beams from two emittersdetected by one receiver, in accordance with an embodiment of thepresent invention. Shown in FIG. 24 are wide beams, one from emitter 201and another from emitter 202, that are both detected at receiver 302.The left and right sides of the one beam are marked 145 and 146,respectively, and the left and right sides of the other beam are marked147 and 148, respectively. The shaded area in FIG. 24 indicates the areaon display 636 at which a touch blocks a portion of both wide beams. Assuch, a touch in this area is detected by two emitter-receiver pairs;namely, 201-302 and 202-302.

Reference is now made to FIG. 25, which is a diagram of the electronicdevice 826 of FIG. 22, showing that points on the screen are detected byat least two emitter-receiver pairs, in accordance with an embodiment ofthe present invention. FIG. 25 shows the wide beams of FIGS. 23 and 24,and illustrates that touches in the shaded wedges on display 636 aredetected by at least two emitter-receiver pairs. The twoemitter-receiver pairs are either one emitter with two receivers, as inFIG. 23, or two emitters with one receiver, as in FIG. 24. Morespecifically, touches that occur near the row of emitters are generallydetected by the former, and touches that occur near the row of detectorsare generally detected by the latter. By surrounding the screen withsimilarly arranged emitters, lenses and receivers, any point may besimilarly detected by two emitter-receiver pairs.

Reference is made to FIG. 26, which is a simplified diagram of awide-beam touch screen, showing an intensity distribution of a lightsignal, in accordance with an embodiment of the present invention. Shownin FIG. 26 is a wide angle light beam emitted by emitter 201 into lens439. The light beam crosses over display 636 and substantially spanslenses 441 and 442. The light is detected at receivers 301 and 302.

Shown in FIG. 26 is a graph of detected light intensity. Total detectedlight corresponds to a shaded area under the graph. An object touchingthe screen blocks a portion of this light. If the object touching thescreen moves across the wide beam, from left to right, the amount ofblocked light increases, and correspondingly the total detected lightdecreases, as the object progresses from the left edge of the beam tothe center of the beam. Similarly, the amount of blocked lightdecreases, and correspondingly the total detected light increases, asthe object progresses from the center of the beam to the right edge ofthe beam.

It is noted that the detected light intensities at the edges of thelight beam are strictly positive, thus ensuring that a touch at theseedges is detected.

Reference is made to FIG. 27, which is a simplified diagram of awide-beam touch screen, showing intensity distributions of overlappinglight signals from two emitters, in accordance with an embodiment of thepresent invention. FIG. 27 shows light detected from emitters 201 and202. A touch point 980 on display 636 blocks light from these emittersdifferently. Area 973 indicates attenuation of light from emitter 201 bypoint 980, and the union of areas 973 and 974 corresponds to theattenuation of light from emitter 202 by point 980. By comparing thelight attenuation the two emitter-receiver pairs, 201-302 and 202-302, aprecise touch coordinate is determined.

Reference is made to FIG. 28, which is a simplified diagram of awide-beam touch screen, showing intensity distributions of two sets ofoverlapping light signals from one emitter, in accordance with anembodiment of the present invention. As shown in FIG. 28, touch point980 is inside the area detected by emitter-receiver pair 201-301 andemitter-receiver pair 201-302. The attenuation of the light signal atreceiver 302, depicted as area 976, is greater than the attenuation atreceiver 301, depicted as area 975. By comparing the light attenuationin the two emitter-receiver pairs, 201-301 and 201-302, a precise touchcoordinate is determined.

Determining the position of touch point 980 requires determining aposition along an axis parallel to the edge along which the emitters arepositioned, say, the x-axis, and along an axis perpendicular to theedge, say, the y-axis. In accordance with an embodiment of the presentinvention, an approximate y-coordinate is first determined and then,based on the expected attenuation values for a point having the thusdetermined y-coordinate and based on the actual attenuation values, aprecise x-coordinate is determined. In turn, the x-coordinate thusdetermined is used to determine a precise y-coordinate. In cases wherethe touch point 980 is already touching the screen, either stationary orin motion, previous x and y coordinates of the touch point are used asapproximations to subsequent x and y coordinates. Alternatively, onlyone previous coordinate is used to calculate a first subsequentcoordinate, with the second subsequent coordinate being calculated basedon the first subsequent coordinate. Alternatively, previous coordinatesare not used.

Reference is made to FIG. 29, which is a simplified diagram of awide-beam touch screen with emitter and receiver lenses that do not havemicro-lens patterns, in accordance with an embodiment of the presentinvention. Shown in FIG. 29 is an electronic device 826 with a display636, emitters 201 and 202, corresponding emitter lenses 439 and 440,receivers 301, 302 and 303, and corresponding receiver lenses 441, 442and 443. Two light beams, 151 and 152, from respective emitters 201 and202, arrive at a point 977 that is located at an outer edge of lens 442.Since beams 151 and 152 approach point 977 at different angles ofincidence, they do not converge on receiver 302. Specifically, lightbeam 152 arrives at receiver 302, and light beam 151 does not arrive atreceiver 302.

In order to remedy the non-convergence, a fine pattern of micro-lensesis integrated with the receiver lenses, at many points long the surfacesof the lenses. The micro-lenses distribute incoming light so that aportion of the light arriving at each micro-lens reaches the receivers.In this regard, reference is made to FIGS. 30 and 31, which aresimplified diagrams of a wide-beam touch screen with emitter anddetector lenses that have micro-lens patterns, in accordance with anembodiment of the present invention. FIG. 30 shows incoming beam 151being spread across an angle θ by a micro-lens at location 977, thusensuring that a portion of the beam reaches receiver 302. FIG. 31 showsincoming beam 152 being spread across an angle ψ by the same micro-lensat location 977, thus ensuring that a portion of this beam, too, reachesreceiver 302. By arranging the micro-lenses at many locations along eachreceiver lens, light beams that enter the locations from differentangles are all detected by the receiver. The detected light intensitiesare communicated to a calculating unit 770 coupled with the receiver.

Reference is made to FIG. 32, which is a simplified diagram of awide-beam touch screen with emitter and receiver lenses that do not havemicro-lens patterns, in accordance with an embodiment of the presentinvention. Shown in FIG. 32 is an electronic device 826 with a display636, emitters 201 and 202, corresponding emitter lenses 439 and 440,receivers 301, 302 and 303, and corresponding receiver lenses 441, 442and 443. Two light beams emitted by emitter 201 and detected byrespective receivers 301 and 302, are desired in order to determine aprecise location of touch point 980. However, lens 439, withoutmicro-lens patterns, cannot refract a beam crossing point 980 toreceiver 301. I.e., referring to FIG. 32, lens 439 cannot refract beam153 as shown. Only the beam shown as 154, crossing point 980, isdetected.

In order to remedy this detection problem, micro-lenses are integratedwith the emitter lenses at many points along the surface of the lenses.The micro-lenses distribute outgoing light so that a portion of thelight reaches the desired receivers. In this regard, reference is madeto FIG. 33, which is a simplified diagram of a wide beam touch screen,with emitter and receiver lenses that have micro-lens patterns, inaccordance with an embodiment of the present invention. FIG. 33 showsthat a portion of light exiting from micro-lens location 982 reachesmultiple receivers. As such, a touch at point 980 is detected byreceivers 301 and 302. It will be noted from FIGS. 32 and 33 that thebeams passing through point 980 are generated by micro-lenses atdifferent locations 981 and 982. Light intensity values detected by thereceivers of FIGS. 32 and 33 are communicated to a calculating unit 770.

Micro-lens patterns integrated with emitter and receiver lenses thusgenerate numerous overlapping light beams that are detected. Each pointon the touch screen is traversed by multiple light beams from multiplemicro-lenses, which may be on the same emitter lens. The micro-lensesensure that the multiple light beams reach the desired receivers.Reference is made to FIG. 34, which is a simplified diagram of twoemitters, 201 and 202, with respective lenses, 439 and 440, that havemicro-lens patterns 444 integrated therein, in accordance with anembodiment of the present invention. Reference is also made to FIG. 35,which is a simplified diagram of two receivers, 301 and 302, withrespective lenses, 439 and 440, that have micro-lens patterns 444integrated therein, in accordance with an embodiment of the presentinvention.

In some cases it is of advantage to avoid having micro-lenses on theoutermost surfaces of the emitter and receiver lenses. Since theoutermost surfaces are visible to a user, it may be less aesthetic tohave the micro-lenses on these surfaces, in order that the visiblesurfaces appear smooth. Moreover, outermost surfaces are susceptible toscratching and to accumulation of dust and dirt, which can degradeperformance of the micro-lenses. As such, in embodiments of the presentinvention, the micro-lenses are integrated on surfaces that are notexposed to the user, as shown below in FIGS. 36, 37 and 40.

Reference is made to FIG. 36, which is a simplified diagram of a sideview of a single-unit light guide, in the context of an electronicdevice having a display and an outer casing, in accordance with anembodiment of the present invention. Shown in FIG. 36 is a cut-away of aportion of an electronic device with a display screen 637, an outercasing 827 above screen 637, and an emitter 200 below screen 637. Alight guide 450 receives light beams 100 and reflects them above screen637 so that they travel across the surface of screen 637 for detection.Light guide 450 includes internal reflective surfaces 451 and 452 forprojecting light beams 100 above the surface of screen 637. A section445 of light guide 450 serves as a primary lens to collimate light beams100 when they are received. The surface of section 445 that facesemitter 200, indicated in bold, has patterns of micro-lenses etchedthereon. As such, the micro-lenses are not visible to a user, and areprotected from damage and dirt.

The surface of section 445 has a feather pattern for scattering incominglight beams 100 from an emitter 200. Reflective surfaces 451 and 452reflect light beams 100. Reflective surface 451 is concave, andreflective surface 452 is a flat reflector oriented at a 45° angle withrespect to incoming light beams 100.

Light beams 100 exit light guide 450 through flat surface 453. Surface454 serves to connect light guide 450 to outer casing 827. Surface 454is located above the plane of active light beams used by the touchsystem, and is angled for aesthetic purposes.

The reflective characteristics of surface 452 require that dust and dirtnot accumulate on surface 452, and require that outer casing 827, whichmay be made inter alia of metal or plastic, not make contact withsurface 452; otherwise, reflectivity of surface 452 may be impaired. Assuch, outer casing 827 is placed above surface 452, thereby protectingsurface 452 from dust and dirt, and outer casing 827 is not flush withsurface 452, so that casing material does not touch surface 452. Being aflat reflector at a 45° angle relative to incoming light beams, surface452 is positioned above the upper surface of display 637. As such, thedevice height, H3, above display 637 due to light guide 450, comprisesthe height, H1, of surface 452 plus the thickness, H2, of outer casing827.

At the receiving side, a light guide similar to 450 is used to receivelight beams 100 that are transmitted over screen 637, and to direct themonto corresponding one or more receivers. Thus, light beams enter lightguide 450 at surface 453, are re-directed by surface 452 and then bysurface 451, and exit through the micro-lens patterned surface ofsection 445 to one or more receivers. At the receiving side, the surfaceof section 445 has a pattern that scatters the light beams as describedhereinabove.

Reference is made to FIG. 37, which is a simplified diagram of sideviews, from two different angles, of a lens with applied featherpatterns on a surface, in accordance with an embodiment of the presentinvention. Shown in FIG. 37 is a light guide 455 having an internalreflective section 456, an internal collimating lens 457, and etchedmicro-lenses 458. Light beams 101 entering light guide 455 at lens 457exit the light guide through a surface 459 as light beams 105.

Similar light guides are used for receiving beams that have traversedthe screen, to focus them onto receivers. In this case, light beamsenter at surface 459, are reflected below the screen surface by internalreflective section 456, are re-focused onto a receiver by collimatinglens 457, and re-distributed by micro-lenses 458. In general, the samelens and micro-lenses are used with an emitter and a detector, in orderthat the light beam be directed at the receiving side in reverse to theway it is directed at the emitting side.

Collimating lens 457 has a rounded bottom edge, as shown at the bottomof FIG. 37. In order to properly refract incoming light on the emitterside, the micro-lenses 458 are formed in a feather pattern, spreading asa fan, as shown at the bottom of FIG. 37 and in FIG. 38.

Reference is made to FIG. 38, which is a simplified diagram of a portionof a wide-beam touch screen, in accordance with an embodiment of thepresent invention. A feather pattern 460 is shown applied to the surfaceof a lens 461. A similar neighboring lens is associated with an emitter200 emitting a wide beam 158.

Reference is made to FIG. 39, which is a top view of light beamsentering and exiting micro-lenses etched on a lens, in accordance withan embodiment of the present invention. Substantially collimated lightbeams 101 are shown in FIG. 39 entering micro-lenses 462 and beingrefracted to light beams 102, such that each micro-lens acts as a lightsource spreading a wide beam across a wide angle.

Touch Screen System Configuration No. 3

Several challenges arise in the manufacture of the micro-lenses inconfiguration no. 2. One challenge is the difficulty of accuratelyforming the fan-shaped feather pattern of micro-lenses. It is desirableinstead to use micro-lenses arranged parallel to one another, instead ofthe fan/feather pattern.

A second challenge relates to the mold used to manufacture the lightguide in configuration no. 2. Referring to FIG. 36, it is desirable thatthe outer surface of section 445, facing emitter 200, be vertical, sothat the front surface of section 445 is parallel with the straight backsurface portion of light guide 450. However, it is difficult tomanufacture exactly parallel surfaces. Moreover, if the light guide 450were to be wider at its bottom, then it would not be easily removablefrom its mold. As such, the two surfaces generally form a wedge, and thesurface of section 445 facing emitter 200 is not perfectly vertical. Tocompensate for this, the micro-lenses are arranged so as to beperpendicular to a plane of incoming light beams.

A third challenge is the constraint that, for optimal performance, themicro-lenses be positioned accurately relative to their correspondingemitter or receiver. The tolerance for such positioning is low. As such,it is desirable to separate section 445 of the light guide so that itmay be positioned accurately, and to allow more tolerance for theremaining portions of the light guide as may be required during assemblyor required for robustness to movement due to trauma of the electronicdevice.

Configuration no. 3, as illustrated in FIGS. 40-42 and 48, serves toovercome these, and other, challenges.

Reference is made to FIG. 40, which is a simplified diagram of a sideview of a dual-unit guide, in the context of an electronic device havinga display 637 and an outer casing 827, in accordance with an embodimentof the present invention. Shown in FIG. 40 is an arrangement similar tothat of FIG. 36, but with light guide 450 split into an upper portion463 and a lower portion 464. The micro-lenses are located at an uppersurface 466 of lower portion 464. As such, the micro-lenses are notembedded in the collimating lens portion of light guide 464.

In configuration no. 2, the curved shape of the collimating lensnecessitated a fan/feather pattern for the micro-lenses etched thereon.In distinction, in configuration no. 3 the micro-lenses are etched onrectangular surface 466, and are arranged as parallel rows. Such aparallel arrangement, referred to herein as a “tubular arrangement”, isshown in FIG. 42. Specifically, a parallel series of micro-lenses 467are shown along an upper surface of light guide 464 in FIG. 42.

An advantage of configuration no. 3 is that the flat upper surface ofthe light guide may be molded as nearly parallel with the screen surfaceas possible, since the mold is one flat surface that lifts off the topof light guide 464. Furthermore, in configuration no. 3, only portion464 of the light guide has a low tolerance requirement for positioning.Portion 463 has a higher tolerance, since its surfaces are not placed ata focal point of an element.

As shown in FIG. 40, light beams 100 emitted by emitter 200 enter lightguide unit 464 at surface 465, are reflected by reflective surface 451through surface 466, and into light guide unit 463. Inside light guideunit 463, light beams 100 are reflected by surface 452, and exit throughsurface 453 over display 637.

FIG. 40 indicates that the height, H3, added by the light guide overdisplay 637 comprises the sum of the height, H1, of internal reflectivesurface 452, and the height, H2, of the thickness of outer casing 827.

Reference is made to FIG. 41, which is a picture of light guide units463 and 464, within the content of a device having a PCB 700 and anouter casing 827, in accordance with an embodiment of the presentinvention. The tubular pattern on the upper surface of light guide unit464 is a fine pattern. In order for this pattern to distribute the lightbeams correctly, light guide 464 is placed precisely relative to itsrespective LED or PD. By contrast, light guide unit 463 has a flatreflective surface and, as such, does not require such precisionplacement. FIG. 40 indicates the relative positioning of light guideunits 463 and 464. Their alignment is represented by a distance 523, andhas a tolerance of up to 1 mm. A distance 522 represents the heightbetween the light guide units.

Reference is made to FIG. 42, which is a top view of light guide units463 and 464 of FIG. 41, in accordance with an embodiment of the presentinvention. Tubular pattern 467 appears on the upper surface of lightguide unit 464.

Touch Screen System Configuration No. 4

Configuration no. 4 uses a reflective light guide and lens that reducethe height of a light guide above a display. The reflective light guideand lens of configuration 4 are suitable for use with the featherpattern lenses of configuration no. 2 and with the tubular patternlenses of configuration no. 3. Many electronic devices are designatedwith a display surface that is flush with the edges of the devices. Thisis often an aesthetic feature and, as such, when integrating opticaltouch screens with electronic devices, it is desirable to minimize oreliminate the raised rims. Less visibly prominent rims result insleeker, more flush outer surfaces of the devices.

Moreover, in optical touch screens, the raised rim occupies a widtharound the display, beyond the edges of the display. Many electronicdevices are designed with display surfaces that seamlessly extend to theedges of the devices. This is often an aesthetic feature and, as such,when integrating optical touch screens with electronic devices, it isdesirable to design the reflective raised rims in such a way that theyappear as seamless extensions of the display.

Configuration no. 4 achieves these objectives by reducing bezel heightand providing a seamless transition between a display edge and an outerborder of a device, resulting in a more appealing aesthetic design. Thelight guide of configuration no. 4 integrates with an outer casinghaving an elongated rounded edge, thereby softening sharp angles andstraight surfaces.

Configuration no. 4 employs two active mirror surfaces; namely, aparabolic reflective surface that folds and focuses incoming light to afocal location, and an elliptical refractive surface that collects lightfrom the focal location and collimates the light into beams across thescreen.

Reference is made to FIG. 43, which is a simplified diagram of a sideview of a light guide within an electronic device, in accordance with anembodiment of the present invention. Shown in FIG. 43 is a light guide468 between an outer casing 828 and a display 637. Light beams from anemitter 200 enter light guide 468 through a surface 445. A featherpattern of micro-lenses is present on a lower portion of surface 445, inorder to scatter the light beams 100. Light beams 100 are reflected byan internal concave reflective surface 469 and by a parabolic reflectivesurface 470, and exit light guide 468 through an elliptical refractivesurface 471. Elliptical refractive surface 471 redirects at least aportion of light beams 100 in a plane parallel with the surface ofdisplay 637. Light beams 100 are received at the other end of display637, by a similar light guide that directs the beams onto a lightreceiver 300. The light intensity detected by light receiver 300 iscommunicated to a calculating unit 770.

Reference is made to FIG. 44, which is a simplified diagram of a sideview cutaway of a portion of an electronic device and an upper portionof a light guide with at least two active surfaces for folding lightbeams, in accordance with an embodiment of the present invention. Shownin FIG. 44 is an upper portion of a light guide 472. Surface 473 is partof a parabola, or quasi-parabola, or alternatively is a free form,having a focal line 475. Focal line 475, and surfaces 473 and 474 extendalong the rim of display 637. Surface 474 is part of an ellipse, orquasi-ellipse, or alternatively a free form, having focal line 475.

On the emitter side, light beams enter the light guide, and parabolicmirror 473 reflects the beams to a focal point inside the light guide.Refracting elliptical lens 474 has the same focal point as parabolicmirror 473. Elliptical lens 474 refracts the light from the focal pointinto collimated light beams over display 637. On the receiver side,collimated light beams enter the light guide, and are refracted byelliptical lens 474 into a focal point. Parabolic mirror 473 reflectsthe beams from the focal point inside the light guide, to collimatedoutput beams.

Surface 469 in FIG. 43 folds light beams 100 upwards by 90°. Surface 469is formed as part of a parabola. In one embodiment of the presentinvention, surface 469 is corrected for aberrations due to input surface445 being slightly inclined rather than perfectly vertical, and also dueto the light source being wider than a single point.

Surfaces 469 and 470 use internal reflections to fold light beams. Thusthese surfaces need to be protected from dirt and scratches. In FIG. 44,surface 473 is protected by outer casing 829. The lower surface (nowshown) of light guide 472 is deep within the electronic device, and isthus protected.

Using configuration no. 4, substantially all of reflective surface 473is located below the upper surface of display 637. Thus, thisconfiguration adds less height to an electronic device than doesconfiguration no. 2. Referring back to FIG. 43, the height, H3′, addedby the light guide in the present configuration is approximately thethickness, H2, of the outer casing, which is less than the correspondingheight, H3, in configuration no. 2. Moreover, the convex shape ofsurface 471 of FIG. 43 and surface 474 of FIG. 44 is easier for a userto clean than is the perpendicular surface 453 of FIG. 36. Thus a usercan easily wipe away dust and dirt that may accumulate on display 637and on surface 471. It is noted that configuration no. 4 eliminates theneed for surface 454 of FIG. 36, since outer casing 828 is flush withthe height of surface 471, instead of being above it.

The convex shape of surface 471 of FIG. 43 makes the bezel less visiblyprominent than does the perpendicular surface 453 of FIG. 36.

Some electronic devices are covered with a flat sheet of glass thatextends to the four edges of the device. The underside of the glass ispainted black near the devices edges, and the display is viewed througha clear rectangular window in the middle of the glass. Examples of suchdevices include the IPHONE®, IPOD TOUCH® and IPAD®, manufactured byApple Inc. of Cupertino, Calif., and also various models of flat-panelcomputer monitors and televisions. In some cases, the light guidessurrounding the various touch screens described herein may appearnon-aesthetic, due to (a) the light guide being a separate unit from thescreen glass and thus the border between them is noticeable, and (b) thelight guide extending below the screen and thus, even if the undersideof the light guide is also painted black, the difference in heightsbetween the bottom of the light guide and the screen glass isnoticeable. Embodiments of the present invention employ a two-unit lightguide to overcome this problem.

In one such embodiment, the upper unit of the light guide is merged withthe screen glass. In this regard, reference is made to FIG. 45, which isa simplified drawing of a section of a transparent optical touch lightguide 476, formed as an integral part of a protective glass 638 coveringa display 637, in accordance with an embodiment of the presentinvention. A daylight filter sheet 639 on the underside of protectiveglass 638 serves, instead of black paint, to hide the edge of display637, without blocking light beams 100. Light guide 476 has an outerelliptical surface 478 and an inner parabolic surface 477, and mergessmoothly with an outer casing 830. Light beams 100 pass through lightguide 476 as in FIG. 44.

In some cases, the cost of manufacturing a protective glass cover withan integrated reflective lens may be expensive. As such, in analternative embodiment of the present invention, a black object isplaced between the upper and lower units of the light guide. The heightof the black object is aligned, within the electronic device, with theheight of the black paint on the underside of the protective glass. Inthis regard, reference is made to FIG. 46, which is a simplifiedillustration of the electronic device and light guide of FIG. 44,adapted to conceal the edge of the screen, in accordance with anembodiment of the present invention. Shown in FIG. 46 is black paint, oralternatively a daylight filter sheet 641, on the underside ofprotective glass 640, covering display 637. A black plastic element 482is aligned with black paint/daylight filter sheet 641, so that the edgeof protective glass 640 is not discernable by a user. Black plasticelement 482 transmits infra-red light to allow light beams 100 to passthrough.

Reference is made to FIG. 47, which is a simplified diagram of a lightguide 483 that is a single unit extending from opposite an emitter 200to above a display 637, in accordance with an embodiment of the presentinvention. A portion of an outer casing 832 is shown flush with the topof light guide 483. The lower portion of light guide 483 has a featherpattern of micro-lenses 484 to scatter the light beams arriving fromemitter 200. At the receiving side, the light beams exit through thebottom of a light guide similar to light guide 483, towards a receiver.The same feather pattern 484 breaks up the light beams en route to thereceiver.

Reference is made to FIG. 48, which is a simplified diagram of adual-unit light guide, in accordance with an embodiment of the presentinvention. Shown in FIG. 48 is a light guide with an upper unit 485 anda lower unit 486. A portion of an outer casing 832 is flush with the topof light guide unit 485. A display 637 is shown to the right of lightguide unit 485. The top surface of light guide unit 486 has a tubularpattern of micro-lenses 487 to break up light beams arriving from anemitter 200. At the receiving side, the light beams exit through thebottom of a light guide similar to the light guide shown in FIG. 48,towards a receiver. The same tubular pattern 487 breaks up the lightbeams en route to the receiver.

As explained hereinabove with reference to FIGS. 36 and 40, thepositioning of light guide unit 486 with tubular pattern 487 requireshigh precision, whereas the positioning of light guide unit 485 does notrequire such precision. The effect of tubular pattern 487 on the lightbeams depends on its precise placement relative to its respectiveemitter or receiver. The active surfaces in light guide unit 485 aremore tolerant, since they are largely self-contained; namely, they areboth focused on an internal focal line, such as focal line 475 of FIG.44.

Touch Screen System Configuration No. 5

Configuration no. 5 relates to increasing the resolution of an opticaltouch screen, to yield high resolution touch sensitivity throughout anactive screen area, including the edges of the screen. Configuration 5is useful for simplifying the process of integrating touch screencomponents, and minimizing the tolerance chain, for a manufacturer, bypreparing modular blocks containing a lens and an emitter or a receiver.These modular blocks are formed so as to be easily positioned togetherin a row along an edge of a display, for fast assembly of a touchscreen. The high tolerance requirements of placing an emitter orreceiver in exactly the correct position vis-à-vis a lens, are handledduring manufacture of the modular blocks, thus removing the burden ofhigh tolerance assembly from a device manufacturer.

High resolution touch sensitivity is achieved by combining two or moreemitter-receiver pair signals that span a common area, as describedhereinabove with reference to configurations nos. 2 and 3. A techniquefor calculating a precise touch location is described hereinbelow.

Simplified manufacturing is achieved by integrating optical elements andelectronic components into a single unit. As such, complex surfaces maybe gathered into one component, thereby reducing the need for highassembly tolerances.

Reference is made to FIG. 49, which is an illustration of opticalcomponents made of plastic material that is transparent to infraredlight, in accordance with an embodiment of the present invention. Shownin FIG. 49 is an optical component 488 that includes a forward-facingLED 236, and electronics to handle the LED signal. Optical component 488is connected to electrical pads 760 and 761. Optical component 488 isused to transmit collimated light beams combined from two emitters;namely, emitter 235 and emitter 236. Emitter 235 is included in aneighboring optical component 489.

Light beams from emitter 235 exit optical component 489 through atight-fitting surface 491, and enter optical component 488 through atight-fitting surface 490. FIG. 49 shows non-parallel light beams fromemitters 235 and 236 entering a lens 493. Components 488 and 489 aresubstantially identical, and fit together. A device manufacturer canthus use these components as building blocks to create a touch screen,by arranging a series of these building blocks in a row along each edgeof the display. Typically, two adjacent display edges are lined withemitter components, and the other two edges are lined with receivercomponents. However, the emitter and receiver components, being ofsubstantially identical shape, can be positioned together in the samerow.

Lens 493 has several surfaces designed to mix and reflect the light fromthe two sources. In one embodiment of the present invention, lens 493has micro-lenses that spread incoming light in the manner describedhereinabove with reference to the feather and tubular patterns ofconfiguration nos. 2 and 3.

An optical component 494 is similar to optical component 488, exceptthat an LED 237 is side-facing instead of forward-facing. FIG. 49 showscollimated light beams 100 exiting optical component 494. Pins 989 and990 guide optical component 494 on a printed circuit board.

Optical component 495 is optical component 488 as viewed from the front.FIG. 49 shows collimated light beams 100 exiting optical component 495.

Similar optical components (not shown) are also provided for receivinglight beams that traverse the screen surface. For these components, theemitters are replaced by receivers, and the electrical components handlethe receiver signals. Such optical components receive parallel lightbeams that enter a lens, and direct the beams onto two differentreceivers.

Reference is made to FIG. 50, which is a simplified diagram of a sideview of a touch screen with light guides, in accordance with anembodiment of the present invention. Shown in FIG. 50 are a display 642,an optical element 496, a photo diode 394 within optical element 496, anoptical element 497, and an emitter 238 within optical element 497.Optical elements 496 and 497 are connected to a printed circuit board762. Emitter 238 emits non-parallel light beams and, as describedhereinabove with reference to FIG. 49, the non-parallel beams areconverted into collimated beams, or substantially collimated beams,before exiting optical element 497. In an embodiment of the presentinvention, micro-lenses etched, or otherwise formed, on the uppersurface of optical element 497 spread the light beams in the mannerdescribed hereinabove with reference to the tubular pattern ofconfiguration no. 3. The beams 100 that exit optical element 497 aredirected upwards and are reflected over display 642 by a light guide498. The light beams 100 enter a light guide 499 on the opposite side ofscreen 642, and are reflected below display 642 into optical element496. As described hereinabove, optical element 496 converts the parallellight beams into non-parallel light beams that converge on photo diode394. In one embodiment of the present invention, micro-lenses etched, orotherwise formed, on the upper surface of optical element 496 spread thelight beams in the manner described hereinabove with reference to thetubular pattern of configuration no. 3. In one embodiment of the presentinvention, the light guides 498 and 499 are constructed as a frame thatsurrounds display 642.

In the touch screen of FIG. 50, two types of light beam redirectionoccur. A first redirection redirects light beams differently, either bycollimating beams emitted by an emitter, or by concentrating input lightbeams onto a photo diode sensor. In the systems of FIGS. 36-45 a lensnear the emitter or receiver performs this redirection. A secondredirection uniformly redirects incoming beams at a 90° angle, or foldsincoming light beams into a narrow waist or focus, as describedhereinabove with reference to configuration no. 4.

The first type of redirection requires that the emitter or receiver bepositioned at a specific location relative to the focal point of thelens. As such, the positioning of the emitter and lens, or receiver andlens, is sensitive to variations in placement. Thus the assembly of theemitter or receiver together with its corresponding lens, has a lowtolerance of error. The second type of redirection, involvingreflection, is robust to variations in position of the reflector or thelight guide. Thus assembly of this portion of the light guide has a hightolerance for error.

In accordance with an embodiment of the present invention, the featheror tubular pattern of micro-lenses is included within an optical elementthat contains the emitter or the receiver, such as optical elements 496and 497 of FIG. 50, and optical elements 488 and 489 of FIG. 49.Manufacture of such optical elements supports accurate placement of theemitter or receiver relative to the embedded pattern of micro-lenses ata low cost of manufacturing. By contrast, if the emitter and the lens,or if the receiver and the lens, are separate elements, themanufacturing cost of aligning the emitter or the receiver with thepatterned lenses on a printed circuit board is high.

The light guides that reflect light above the screen surface may bemanufactured separately and assembled with other touch screencomponents. Thus in FIG. 50 light guides 498 and 499 are shown separatefrom optical elements 496 and 497.

Reference is made to FIG. 51, which is an illustration of a touch screenwith a block of three optical components on each side, in accordancewith an embodiment of the present invention. Blocks 500 and 501 areemitters, and blocks 502 and 503 are receivers. The blocks create anactive area 991, where an x-y touch position of a stylus or finger maybe calculated based on detected blocked light. Adding more opticalcomponents of the same type to each block serves to enlarge the activearea that is created.

Reference is made to FIG. 52, which is a magnified illustration of oneof the emitter blocks of FIG. 51, in accordance with an embodiment ofthe present invention. Shown in FIG. 52 are three emitters 239, 240 and241, that emit respective wide beams 167, 168 and 169 from one edge of ascreen, which are read as respective signals 170, 171 and 172. At theopposite edge of the screen, signals 170, 171 and 172 are eachredirected onto at least two adjacent receivers by respective opticalcomponents. An accurate position of an object, such as a finger orstylus, touching the screen, is then determined based on values ofblocked light at the receivers, as described below with respect to FIG.81.

Touch Screen System Configuration No. 6

Configuration no. 6 uses a reduced number of components by coupling anemitter or a receiver to one end of a long thin light guide situatedalong an edge of the screen. Such a light guide is described in U.S.Pat. No. 7,333,095 entitled ILLUMINATION FOR OPTICAL TOUCH PANEL.

Reference is made to FIG. 53, which is an illustration of a touch screenhaving a long thin light guide 514 along a first edge of the screen, fordirecting light over the screen, and having an array of light receivers300 arranged along an opposite edge of the screen for detecting thedirected light, and for communicating detected light values to acalculating unit 770, in accordance with an embodiment of the presentinvention. Light emitters 200 are coupled to both ends of light guide514. Light guide 514 is positioned along one edge of a touch screen 800.Light is emitted into light guide 514 along a screen edge, and isre-directed across the screen surface by a reflector 515. A plurality ofreceivers 300 is situated along the opposite edge of touch screen 800,to enable multiple receivers to detect a touch, as described hereinabovewith reference to configuration nos. 2 and 3.

Reference is made to FIG. 54, which is an illustration of a touch screenhaving an array of light emitters 200 along a first edge of the screenfor directing light beams over the screen, and having a long thin lightguide 514 for receiving the directed light beams and for furtherdirecting them to light receivers 300 situated at both ends of lightguide 514, in accordance with an embodiment of the present invention.Detected light values at receiver 300 are communicated to a calculatingunit (not shown). According to another embodiment of the presentinvention, only one light receiver 300 is coupled to one end of lightguide 514. Light guide 514 is positioned along one edge of a touchscreen 800. A plurality of emitters is situated along the opposite edgeof the touch screen, to enable receiver(s) 300 to detect a touch basedon serial activation of multiple emitters, as described hereinabove withreference to configuration nos. 2 and 3. Light emitted across the screensurface is re-directed by a reflector 515. Light is received into lightguide 514 along the screen edge and is directed through the length oflight guide 514 onto a receiver 300.

Reference is made to FIG. 55, which is an illustration of two lightemitters, 201 and 202, each emitter coupled to an end of a long thinlight guide 514, in accordance with an embodiment of the presentinvention. Light guide 514 is positioned along one edge of a touchscreen. Light 100 is emitted into light guide 514 along a screen edge,and is re-directed across the screen surface by a reflector 515. Aplurality of receivers is situated along the opposite edge of the touchscreen, to enable multiple receivers to detect a touch, as describedhereinabove with reference to configuration nos. 2 and 3. Each emitter201 and 202 is activated separately, and the receivers thus detect atouch based on blocked light from each of the two emitters. The amountof light 100 emitted at any given location along the length of the lightguide decreases as a function of the distance between the location andthe emitter. As such, different amounts of detected light from eachemitter 201 and 202 are used to calculate the precise location of atouch, as described hereinabove with reference to configuration nos. 2and 3.

Embodiments of the present invention improve upon the light guide ofU.S. Pat. No. 7,333,095, by etching or otherwise forming micro patterns516 on the outer surface of the light guide, in order to widely refractoutgoing light beams 101 of FIG. 53, or incoming light beams 102 of FIG.54, as described hereinabove with reference to configuration nos. 2 and3. Micro patterns 516 are a uniform substantially parallel pattern ofgrooves along light guide 514, and are simpler to form than the fanpattern described hereinabove with reference to configuration no. 2.Light guide 514 also includes a light scatterer strip 517 inside oflight guide 514. Micro patterns 516 and light scatterer strip 517 appearin FIGS. 53 and 54.

Touch Screen System Configuration No. 7

Configuration no. 7 enables detecting pressure on a touch screen, asapplied during a touch operation. Detecting pressure enablesdiscrimination between a light touch and a hard press, and is useful foruser interfaces that associate separate actions to a touch and a press.E.g., a user may select a button or icon by touching it, and activatethe function associated with the button or icon by pressing on it. Sucha user interface is described in applicants' co-pending U.S. applicationSer. No. 12/486,033, entitled USER INTERFACE FOR MOBILE COMPUTER UNIT.

In some embodiments of the present invention, a touch enabled deviceincludes a base plane, such as a PCB, a light guide frame rigidlymounted on the base plane, and a resilient member attached to the baseplane to suspend or “float” a non-rigidly mounted touch screen insidethe light guide frame. A press on the touch screen deflects the floatingtouch screen along a z-axis, exposing more of the light guide frame. Alight guide frame reflector, which directs light over the screen asdescribed hereinabove, is formed so that the exposure allows more lightto traverse the screen. In this way, when a hard press on the screenoccurs, many of the receivers detect a sudden increase in detectedlight. Moreover, detection of a hard press may be conditioned upon atouch being detected at the same time, thus preventing false detectionof a hard press due to a sudden increase in ambient light. When thedownward pressure is released, the resilient member returns the screento its original position within the light guide frame.

Reference is made to FIGS. 56-59, which are illustrations of a touchscreen 800 that detects occurrence of a hard press, in accordance withan embodiment of the present invention. FIG. 56 shows touch screen 800in rest position, screen 800 being supported by resilient supportingmembers 841 and 842 that create a flex air gap 843, which are mounted ona printed circuit board 700. FIG. 56 shows two light guides, 518 and519, one on either side of screen 800, for directing light 100 from anemitter 200 over screen 800 to a receiver 300. Only a small upperportion of each light guide 518 and 519 extends above screen 800.Receiver 300 communicates detected light intensities to a calculatingunit 770.

FIG. 57 shows a finger 900 pressing down on the screen, causing members841 and 842 to compress and to narrow flex air gap 843. As a result, alarger portion of light guides 518 and 519 are exposed above screen 800,thus allowing (a) more light 100 from emitter 200 to traverse screen 800and be detected by receiver 300, and (b) more ambient light 101 to reachreceiver 300. In various embodiments, either or both of these increasesin detected light are used to indicate a hard press. In otherembodiments, the amount of downward pressure applied is determined basedon the amount of additional detected light, thus enabling discriminationbetween more hard and less hard touches.

In some embodiments, the light guide frame includes protruding lips 520and 521, shown in FIG. 58, that extend over the edges of screen 800, tocounter balance the upward force of resilient members 841 and 842 whenno downward pressure is applied to screen 800. Resilient members 841 and842 may comprise inter alia a flexible mounting material, a torsionspring, an elastic polymer body, or a hydraulic suspension system. FIG.59 shows emitters 200, receivers 300 coupled with calculating unit 770,and resilient members 841 and 842 arranged on a single PCB 700.

In other embodiments, the touch screen is not displaceable relative tothe frame. However, the screen flexes or bends somewhat in response to ahard press. The bending of the screen causes a sudden increase indetected light in many of the receivers, indicating a hard press on thescreen. As indicated hereinabove, detection of a hard press may beconditioned upon a touch also being detected at the same time, thuspreventing false detection of a hard press in response to trauma to thedevice.

Reference is made to FIGS. 60 and 61, which are bar charts showingincrease in light detected, when pressure is applied to a rigidlymounted 7-inch LCD screen, in accordance with an embodiment of thepresent invention. The bar charts show the amount of light detected fromeach emitter along one edge of the screen when a soft touch occurs (FIG.60), and when a hard touch occurs (FIG. 61). The light emitters andlight receivers are shift-aligned, so that light from each emitter isdetected by two receivers. As such, two bars are shown for each emitter,indicating the light detected by each of the two receivers. Both barsindicate that a touch is detected at receivers opposite LED 4, where nolight is detected. The bar charts show that more light is detected fromneighboring emitters in the case of a hard touch, than in the case of asoft touch.

Touch Screen System Configuration No. 8

Configuration no. 8 provides a touch screen with at least one camerapositioned under the screen surface, to capture an image of the screensurface and of a pointer, or a plurality of pointers, touching thescreen surface. In some embodiments of the present invention, the screenpixels include light sensors, each of which generates a pixel of animage of the underside of the screen glass, the image being referred toherein as the “screen glass image”.

As described hereinbelow, methods according to embodiments of thepresent invention determine precise touch coordinates using spatial andtemporal filters. Application of these methods to configuration no. 8yields sub-pixel precision for touch coordinates.

Pixels in the screen glass image at the center of a touch location aregenerally completely blocked; i.e., the level of light detected at eachsuch pixel is below a designated threshold, indicating that the pixel isoccluded by a touch object. Pixels in the screen glass image along theedges of a touch location are generally only partially blocked; i.e.,the level of light detected at each such pixel is above the designatedthreshold, indicating that the pixel is only partially occluded by thetouch object.

A calculating unit that receives the screen glass image data assigns arelative weight to each pixel coordinate, based on a touch detectionintensity associated with that pixel, as indicated by the pixel's value.The calculating unit further interpolates the pixel coordinates, basedon their associated weights, to determine a touch coordinate. In someembodiments, the calculating unit calculates a touch area having aperimeter, wherein the edges of the touch area are calculated on asub-pixel level based on the above interpolations. The temporal filtersdescribed hereinbelow are applied inter alia when a series of connectedtouches are concatenated into a glide movement over a time duration.

Reference is made to FIG. 62, which is a simplified diagram of an imagesensor 844 positioned beneath a screen glass display 635, to capture animage of the underside of the screen glass and of touches made thereon,in accordance with an embodiment of the present invention. The capturedimage data is transmitted to a calculating unit 770 for analysis.

Reference is made to FIG. 63, which is a simplified diagram of a display635 divided into pixels, and three touch detections 906-908, inaccordance with an embodiment of the present invention. It is noted thatedges of each of the touch detections cover respective portions ofpixels. The weighted pixel coordinate interpolations describedhereinabove are used to identify touch coordinates, such as coordinatesfor touches 906 and 907, and the contours of touch areas, such as thecontours of areas 907 and 908. In some embodiments of the presentinvention, the interpolations include fully occluded pixels. In otherembodiments of the present invention, the interpolations include onlypartially occluded pixels.

Touch Screen System Configuration No. 9

Configuration no. 9 provides a touch screen with means to determine athree-dimensional position of a pointer relative to the touch screen. Inthis configuration, a low cost touch screen uses cameras to determinedepth information. One or more cameras are mounted on a side of thetouch screen, so as to capture a mirrored image of an active touch area,and the mirrored image is processed to determine a height of the pointerabove the touch screen. The present invention may be embodied on anarbitrary size touch screen having a glossy surface.

Reference is made to FIG. 64, which is a simplified diagram of a camerasensor 844 positioned on a hinge 771 of a laptop computer 848, andpointing at a screen 643, in accordance with an embodiment of thepresent invention.

Reference is made to FIG. 65, which is a simplified side view diagramshowing a camera 844 viewing a touch area 992, in accordance with anembodiment of the present invention.

Reference is made to FIG. 66, which is a simplified top view diagramshowing a camera 844 viewing a touch area 992, in accordance with anembodiment of the present invention. The broken lines in FIG. 66indicate the volume of space captured by camera 844.

Reference is made to FIG. 67, which is a simplified diagram of a camera844 viewing a touch area 992, and two image axes, an image x-axis and animage y-axis, for locating a touch pointer based on an image captured bycamera 844, in accordance with an embodiment of the present invention.Reference is also made to FIG. 68, which is a simplified diagram of acamera 844 viewing a touch area 992, and two screen axes, a screenx-axis and a screen y-axis, for locating a touch pointer based on animage captured by camera 844, in accordance with an embodiment of thepresent invention. The screen surface along the line of vision capturedby camera 844 is oriented along the image y-axis. The image x-axis isperpendicular to the image y-axis along the plane of the touch screensurface. In order to distinguish these axes from the screen axes thatrun parallel to the screen edges, the former axes are referred to hereinas “image axes”, and the latter axes are referred to herein as “screenaxes”. Touch coordinates relative to the image axes may be transformedto screen axis coordinates.

The image captured by camera 844 generally includes both a pointer, anda reflection of the pointer on the surface of the touch screen. Based onthe locations of the pointer and its reflection within the capturedimage, the pointer position may be determined when the pointer ispositioned on the screen, or even above the screen. When the pointertouches the screen, the pointer and its reflection in the captured imageare tangent to one another, as illustrated in FIGS. 73-75. When thepointer is above the screen, the pointer and its reflection in thecaptured image are separated apart from one another, as illustrated inFIG. 76.

It will be appreciated by those skilled in the art that the capturedimage may be analyzed relative to an x-axis along the bottom edge of theimage, and a y-axis in the screen surface along the camera's line ofvision. When the pointer is touching the screen, the pointer's x- andy-coordinates may be determined by projecting the position of a pointerin the captured image along the x- and y-axes.

When the pointer is positioned above the screen, not touching thescreen, the pointer's x-coordinate may be determined as above; namely,by projecting the position of the pointer in the captured image alongthe x-axis. To determine, the pointer's y-coordinate an appropriatelocation is selected along the line joining the positions of the pointerand the reflected pointer in the captured image, and the position of thelocation is projected along the y-axis. In some instances, theappropriate location is the mid-point of the line joining the positionsof the pointer and the reflected pointer. In other instances, theappropriate location is based upon the azimuthal angle at which thecamera is orientated relative to the screen surface.

It will be appreciated by those skilled in the art that the height ofthe pointer above the screen surface may be determined based upon thedistance between the pointer and the pointer's reflection in thecaptured image.

Use of multiple cameras provides additional information, such asmufti-touch information and stylus information that may be obscured by ahand. Reference is made to FIGS. 69 and 70, which are simplifieddiagrams of two cameras, 844 and 845, each capturing a touch area 992from different angles, in accordance with an embodiment of the presentinvention. Each camera has a respective set of image axes, as shown inFIG. 70. Reference is made to FIG. 71, which is a simplified diagram offour cameras, 844-847, each capturing a touch area 992 from differentangles, in accordance with an embodiment of the present invention.

Reference is made to FIG. 72, which is a simplified diagram, from acamera viewpoint, of a camera 844 viewing a complete touch area 992, inaccordance with an embodiment of the present invention. Shown in FIG. 72are the image x- and y-axes, for images captured by camera 844.

Reference is made to FIG. 73, which is a simplified diagram of a portionof a touch area 992 showing a stylus 903 and a mirror image 645 of thestylus, which are tangent to one another, in accordance with anembodiment of the present invention. The image x- and y-coordinates ofstylus 903 are determined by projecting the position of stylus 903 ontothe image x- and y-axes. To assist with the projection, a centerline 996between stylus 903 and its mirror image 645 is used.

Reference is made to FIG. 74, which is a simplified diagram showing astylus 903 and a mirror image 645 of the stylus, moved closer to thecenter of a touch area 992 vis-à-vis FIG. 73, in accordance with anembodiment of the present invention. Again, the image x- andy-coordinates of stylus 903 are determined by projecting the position ofstylus 903 onto the image x- and y-axes. To assist with the projection,a centerline 997 between stylus 903 and its mirror image 645 is used.

Reference is made to FIG. 75, which is a simplified diagram showing astylus 903 and a mirror image 645 of the stylus, moved closer to thebottom of a touch area 992 vis-à-vis FIG. 73, in accordance with anembodiment of the present invention. Again, the image x- andy-coordinates of stylus 903 are determined by projecting the position ofstylus 903 onto the image x- and y-axes. To assist with the projection,a centerline 998 between stylus 903 and its mirror image 645 is used.

Reference is made to FIG. 76, which is a simplified diagram showing astylus 903 and a mirror image 645 of the stylus, separated apart fromone another, in accordance with an embodiment of the present invention.The distance between stylus 903 and mirror image 645 may be used todetermine the height of stylus 903 above touch area 992. A centerline999 between stylus 903 and mirror image 645 is used as an assist todetermine the image y-coordinate of stylus 903.

In accordance with an embodiment of the present invention, stylus 903 inFIGS. 73-76 is a blunt-edged stylus. A blunt-edged stylus is ofadvantage, as its relatively large head is easy to detect by imageprocessing. A blunt-edged stylus is also of advantage in configurationsnos. 2-6, as its relatively large head blocks more light than does asharp-pointed stylus.

Reference is made to FIG. 77, which is a simplified flowchart of amethod for determining a three-dimensional pointer location, inaccordance with an embodiment of the present invention. At operation1011, an image of a screen surface is captured. The image includes apointer, and a reflection of the pointer on the screen surface, asdescribed hereinabove with reference to FIGS. 73-76. At operation 1012,the pointer location along a first screen axis is determined,corresponding to the location of the pointer in the image along thataxis, as illustrated by the x-coordinates shown in FIGS. 73-75 thatcorrespond to the locations of the stylus in the respective images. Atoperation 1013 the pointer location along a second screen axis isdetermined, corresponding to a line running through the mid-pointbetween the locations of the pointer and its reflection, as illustratedby centerlines 996-999 in FIGS. 73-76. At operation 1014, the height ofthe pointer above the screen is determined, based on the distancebetween the pointer and its reflection in the captured image.

When the camera position is known or fixed, relative to the screen, asis the case inter alia when the screen is manufactured with the camerarigidly mounted, the image-to-screen transformation, from imagecoordinates to screen coordinates, may be determined. When the positionof the camera relative to the screen is unknown, such as is the caseinter alia if the camera is mounted manually by a user, then in order todetermine the image-to-screen transformation a procedure to determinecamera orientation is required. One such procedure is to display aseries of touch icons on the screen at known screen coordinates.Reference is made to FIG. 78, which is a simplified diagram of a toucharea 992 that displays six touch icons 965-970, used for determining acamera orientation, in accordance with an embodiment of the presentinvention. Camera 844 is aimed at the touch area to capture touchevents. A user is instructed to touch the various icons. In someembodiments, each icon is displayed individually one at a time. When theuser touches an icon, the image coordinates of the touch are determined,and matched with the known screen coordinates of the icon. Successivematched pairs of image coordinates and screen coordinates are used todetermine the image-to-screen transformation. In an embodiment of thepresent invention, the event that a user touches an icon is recognizedfrom a captured image when the pointer is tangent to its reflection, asdescribed hereinabove.

Operation of Configurations Nos. 2-8

The following discussion relates to methods of operation forarrangements of the optical elements shown in configurations nos. 2-8,around a touch screen, to achieve accurate touch detection. Thesemethods are of advantage for pen and stylus support, which have finetouch points. In particular, these methods are not required for singletouch finger support. As such, for systems designed with only fingersupport, these methods may be applied without micro-lenses being etchedonto primary lenses. In some cases, such as multi-touch detection, thesemethods apply to finger touch as well.

Reference is made to FIGS. 79 and 80, which are illustrations ofopposing rows of emitter lenses and receiver lenses in a touch screensystem, in accordance with an embodiment of the present invention.Positioned behind each emitter and receiver lens is a correspondingrespective light emitter 200 or light receiver 300. As shown in FIG. 79,each emitter 200 is positioned opposite two receivers 300 that detectlight beams emitted by the emitter. Similarly, each receiver 300 ispositioned opposite two emitters 200, and receives light beams emittedfrom both emitters.

FIG. 79 shows (A) a single, full beam 173 from an emitter 200 that spanstwo receivers 300; (B) the portion of the full beam, designated 174,detected by the left one of the two receivers 300; (C) the portion ofthe full beam, designated 175, detected by the right one of the tworeceivers 300; (D) multiple beams 176, for multiple emitters 200,covering the touch screen, and (E) multiple beams 177, for multipleemitters 200, covering the touch screen. Generally, each emitter 200 isactivated alone. Precision touch detection is described hereinbelow,wherein a touch point is detected by multiple beams. It will beappreciated from (D) and (E) that points on the screen are detected byat least one beam 176 and one beam 177.

To conserve power, when the touch screen is idle only one set of beams,namely, beams 176 or beams 177, are scanned in a scanning sweep, andonly for the axis with the smallest number of emitters 200. The scanningtoggles between beams 176 and beams 177, and thus two scanning sweepsalong the axis activate every emitter-receiver pair along the axis. Theother axis, with the larger number of emitters, is only scanned wheneither a touch is present, or when a signal differs from its referencevalue by more than an expected noise level, or when an update ofreference values for either axis is being performed. Reference valuesare described in detail hereinbelow.

FIG. 80 shows (A) an emitter 201 sending light to a receiver 301 at anangle of 15° to the left; (B) emitter 201 sending light to a receiver302 at an angle of 15° to the right; (C) emitter 202 sending light toreceiver 302 at an angle of 15° to the left; and (D) a microstructurerefracting incoming light. The emitter lenses and receiver lenses shownin FIG. 80 are equipped with the microstructure shown in (D), in order(i) to emit light in both left and right directions from multiplelocations along the emitter lens surface, and (ii) to ensure that lightreceived at any angle of incidence at any location along the receiverlens surface is detected by the receiver.

Reference is made to FIG. 81, which is a simplified illustration of atechnique for detecting a touch location, by a plurality ofemitter-receiver pairs in a touch screen system, in accordance with anembodiment of the present invention. Shown in FIG. 81 is an opticalemitter lens 506 of width k, positioned opposite two optical receiverlenses 508 and 509, each of width k, on a touch screen. A pointer, 900,touching the screen blocks a portion of the light beam emitted fromoptical emitter lens 506. Optical emitter lens 506 emits overlappingbeams that cover both optical receiver lenses 508 and 509. The spreadangle of the wide beam depends on the screen dimensions, and on the lenswidth, k, along the x-axis. Another optical emitter lens 507 is alsoshown, shifted by half an element width, m, below an optical receiverlens 510.

Similarly, in a system such as the system shown in FIG. 51 having blocks500 and 501 of optical emitter elements positioned opposite blocks 502and 503 of optical receiver elements, the position of each block ofoptical receiver elements may be shifted by half an element distance, inorder that the center of an optical emitter element be aligned with theborder between two optical receiver elements.

In accordance with an embodiment of the present invention, at least onesurface of optical emitter lens 506 is textured with a plurality ofridges. Each ridge spreads a beam of light that spans the two opposingreceiver lenses 508 and 509. As such, light from each of many pointsalong the surface of optical emitter lens 506 reaches both opposingreceiver lenses 508 and 509, and the light beams detected by adjacentreceivers overlap. In configuration no. 2 these ridges form a featherpattern, and in configuration no. 3 these ridges form a tubular pattern.

In accordance with an embodiment of the present invention, the ridgesform micro-lenses, each having a pitch of roughly 0.2-0.5 mm, dependingon the touch screen configuration. In the case of a feather pattern, theridges form a fan, and their pitch narrows as the ridges progress inwardand become closer together. In the case of a tubular pattern, the pitchof each micro-lens remains constant along the length of the micro-lens.

At least one surface of each receiver lens 508 and 509 is similarlytextured, in order that at least a portion of light arriving at each ofmany points along the receiver lens surface, arrive at the receiverphoto diode.

In accordance with an embodiment of the present invention, the output xand y coordinates are filtered temporally and spatially. The followingdiscussion relates to determination of the x-coordinate, and it will beappreciated by those skilled in the art that the same method applies todetermination of the y-coordinate.

Configurations nos. 2 and 3 show that a touch location is detected by atleast two emitter-receiver pairs. FIG. 81 shows two suchemitter-receiver pairs, 506-508 and 506-509, detecting a touch locationof object 900 along the x-axis. In FIG. 81, beams 506-508 are denoted bybeam 178, and beams 506-509 are denoted by beam 179. FIG. 81 shows threedetection areas; namely, (i) the screen area detected byemitter-receiver pair 506-508, drawn as a wedge filled withright-sloping lines, (ii) the screen area detected by emitter-receiver506-509, drawn as a wedge with left-sloping lines, and (iii) the screenarea detected by both emitter-receiver pairs 506-508 and 506-509, drawnas a wedge with a crosshatch pattern. The left and right borders of thisthird screen area are shown as lines X₁ and X₂, respectively.

In order to determine the x-coordinate X_(p) of object 900's touchlocation (X_(p), Y_(p)), an initial y-coordinate, Y_(initial), isdetermined corresponding to the location along the y-axis of theemitter-receiver pair having the maximum touch detection signal amongall emitter-receiver pairs along the y-axis. In FIG. 81, thisemitter-receive pair is 507-510. The lines designated X₁ and X₂ in FIG.81 are then traversed until they intersect the line y=Y_(initial) atlocations (X_(a), Y_(initial)) and (X_(b), Y_(initial)). CoordinatesX_(a) and X_(b) are shown in FIG. 81. The x-coordinate of object 900 isthen determined using the weighted average

X _(P)=(W _(a) X _(a) +W _(b) X _(b))/(W _(a) +W _(b)),  (1)

where the weights W_(a) and W_(b) are normalized signal differences forbeam 178 and beam 179, respectively. The signal difference used is thedifference between a baseline, or expected, light value and the actualdetected light value. Such difference indicates that an object istouching the screen, blocking a portion of the expected light.Calibration and normalization of the weights is described hereinbelow. Asimilar weighted average is used to determine the y-coordinate Y_(P).

If the pointer 900 is detected by more than two emitter-receiver pairs,then the above weighted average is generalized to

X _(P)=Σ(W _(n) X _(n))/(ΣW _(n)),  (2)

where the weights W_(n) are normalized signal differences, and the X_(n)are weight positions.

In one embodiment of the present invention, where the pointer 900 is asmall object, the largest signal difference is used in conjunction withthe two closest signals to calculate the position. This compensates forthe fact that the signal differences for small objects are small, andnoise thus becomes a dominant error factor. Use of the two closestsignals reduces error due to noise. In another embodiment of the presentinvention, only the two largest signal differences are used.

Reference is made to FIG. 82, which is an illustration of a light guideframe for the configuration of FIGS. 79 and 80, in accordance with anembodiment of the present invention. Shown in FIG. 82 are four edges ofa light guide frame, with optical emitter lenses 511 and opticalreceiver lenses 512. It is noted that the inner edges of the frame arenot completely covered by beams 182. As such, in some embodiments of thepresent invention only an inner touch area 993, indicated by the dashedrectangle, is used.

To reduce error due to signal noise, the final coordinate is determinedas the output of a temporal filter, using the spatially filtered currentcoordinate value, determined as above, and a previous coordinate value.The higher the filter weight given to the current x-coordinate, thecloser the output will be to that value, and the less will be the impactof the filter. Generally, use of substantially equal weights for bothcoordinate values results in a strong filter. In one embodiment of thepresent invention, the temporal filter is a low-pass filter, but otherfilters are also contemplated by the present invention. In accordancewith an embodiment of the present invention, different pre-designatedfilter weight coefficients may be used in different cases. In analternative embodiment, the filter weight coefficients are calculated asneeded.

Choice of appropriate filter coefficients is based on scanningfrequency, the speed at which a touch object is moving across thescreen, whether the object motion is along a straight line or not, andthe size of the touch object.

Generally, the higher the scanning frequency, the nearer the currentcoordinate value is to the previous coordinate value, and a strongerfilter is used. Scanning frequency is used to estimate the speed anddirection of movement of an object. Based on the scanning frequency, athreshold distance is assigned to two input values, the thresholdindicating fast movement. If the difference between the current andprevious coordinate values is greater than the threshold distance, aweaker filter is used so that the output coordinate not lag considerablybehind the actual touch location. It has been found by experiment thatthe filter

output_val= 1/10*previous_val+ 9/10*current_val  (3)

provides good results in this case. In addition, the lag value,described hereinbelow, is reset to equal the output value in this case.

If the difference between the current and previous coordinate values isless than the threshold distance, then a lag value is determined. Thelag value indicates speed and direction along an axis. In has been foundby experiment that the value

lag=⅚*lag+⅙*current_val  (4)

provides good results in this case. The filter weight coefficients areselected based on the difference between the lag value and the currentcoordinate value. Generally, the greater this difference, whichindicates either fast motion or sudden change in direction, the weakerthe filter.

For example, if the touch object is stationary, the lag value eventuallyis approximately equal to the current coordinate value. In such case,signal noise may cause small differences in the spatially calculatedtouch position, which in turn may cause a disturbing jitter effect;i.e., the touch screen would show the object jittering. Use of a strongtemporal filter substantially dampens such jittering.

If the touch object is moving fast or makes a sudden change indirection, a strong temporal filter may create a perceptible lag betweenthe actual touch location and the displayed touch location. In the caseof a person writing with a stylus, the written line may lag behind thestylus. In such cases, use of a weak temporal filter reduces suchlagging.

When the touch object covers a relatively large screen area, such as afinger or other blunt object touching the screen, the lag between theactual finger motion and the displayed trace of the motion is lessperceptible, because the finger covers the area of the lag. In suchcase, a different temporal filter is used.

The type of object, finger vs. stylus, being used may be inferred byknowing expected user behavior; e.g., a user interface intended forfinger touch assumes a finger being used. The type of object may also beinferred by the shadowed area created by the object. The size of thetouch area as determined based on shadowed emitter signals, is thereforealso a factor used in selecting temporal filter weight coefficients.

Reference is made to FIG. 83, which is a simplified flowchart of amethod for touch detection for an optical touch screen, in accordancewith an embodiment of the present invention. At operation 1021, acurrent coordinate value is received, based on a spatial filter thatprocesses signals from multiple emitter-receiver pairs. A thresholddistance is provided, based on a scan frequency. At operation 1022, thedifference between the current coordinate value and a previouscoordinate value is compared to the threshold distance. If thedifference is less than or equal to the threshold distance, then atoperation 1023 a new lag value is calculated, as in Eq. (4). Atoperation 1024 temporal filter weight coefficients are determined basedon the difference between the current coordinate value and the lagvalue. At operation 1025, the temporal filter is applied to calculate anoutput coordinate value, as in Eq. (3).

If, at operation 1022, the difference between the current coordinatevalue and previous coordinate value is greater than the thresholddistance, then weak filter weight coefficients are selected at operation1026. At operation 1027, the temporal filter is applied to calculate anoutput coordinate value, as in Eq. (3). At operation 1028 the lag valueis set to the output coordinate value.

Embodiments of the present invention provide a method and apparatus fordetecting a mufti-touch operation whereby two touches occursimultaneously at two corners of a touch screen. An example of such amufti-touch is a rotation gesture, shown in FIGS. 84-86, whereby a userplaces two fingers 900 on a screen 800 and turns them around an axis. Aspointed out hereinabove with reference to FIGS. 8 and 9, it is difficultfor a light-based system to discriminate between a top-left &bottom-right touch vs. a bottom-left & top-right touch. Use ofshift-aligned emitters and receivers enables such discrimination, asdescribed hereinbelow.

In accordance with an embodiment of the present invention, data fromreceivers along a first axis is used to determine a touch location alongtwo axes. Reference is made to FIGS. 87-90, which are illustrations of afinger 900 touch event at various locations on a touch screen, andcorresponding FIGS. 91-94, which are respective bar charts of lightsaturation during the touch events, in accordance with an embodiment ofthe present invention. FIG. 87 shows a touch located near a row ofemitters, between two emitters. FIG. 88 shows a touch located near a rowof receivers, blocking a receiver. FIG. 89 shows a touch located near arow of emitters, blocking an emitter. FIG. 90 shows a touch located neara row of receivers, between two receivers.

FIGS. 91-94 each include two bar charts; namely, an upper chart showinglight saturation at receivers along an x-axis, and a lower chart showinglight saturation at receivers along a y-axis. Each row of receivers isshift-aligned with an opposite row of emitters. As such, each emitter isdetected by two receivers. Correspondingly, FIGS. 91-94 show two barsfor each emitter, one bar per receiver.

FIGS. 91-94 exhibit four distinct detection patterns. FIG. 91 shows anabsence of light detected primarily by one receiver from its tworespective emitters. The absence of light is moderate. FIG. 92 shows anabsence of light detected primarily by one receiver from its tworespective emitters. The absence of light is large. FIG. 93 shows twoadjacent receivers detecting a large absence of expected light from theblocked emitter. Both receivers detect some light from neighboringelements. FIG. 94 shows two adjacent receivers detecting a moderateabsence of expected light from the blocked emitter. Both receiversdetect some light from neighboring emitters. TABLE I summarizes thesedifferent patterns.

TABLE I Patterns of touch detection based on proximity to and alignmentwith emitters and receivers No. of Receivers Amount of Pattern No.Detecting the Expected Light FIGS. Touch Location Touch that is Blocked1 Near a row of 1 Moderate FIG. 87 emitters, between FIG. 91 twoemitters 2 Near a row of 1 Large FIG. 88 receivers, blocking FIG. 92 areceiver 3 Near a row of 2 Large FIG. 89 emitters, blocking FIG. 93 anemitter 4 Near a row of 2 Moderate FIG. 90 receivers, between FIG. 94two receivers

According to an embodiment of the present invention, determination oflocation of a multi-touch is based on the patterns indicated in TABLE I.Thus, referring back to FIG. 85, four detection points are shown alongtwo rows of receivers. Detections D1-D4 detect touch points 971 inupper-right & lower-left corners of the screen. Based on whether thedetection pattern of each point is of type 1 or 3, or of type 2 or 4,the detection patterns determine whether the corresponding touch iscloser to the emitters, or closer to the receivers. Each touch has twoindependent indicators; namely, the X-axis detectors, and the Y-axisdetectors. Thus, for detection points 971 in FIG. 85, detections D1 andD3 are of types 2 or 4, and detections D2 and D4 are of types 1 or 3. Indistinction, for detection points 971 in FIG. 86, detections D2 and D4are of types 2 or 4, and detections D1 and D3 are of types 1 or 3.

In addition to evaluation of detection points independently, the variousdetection patterns may be ranked, to determine which touch point iscloser to the emitters or to the receivers.

Moreover, when a rotate gesture is performed, from touch points 971 totouch points 972, movement of detections discriminates whether thegesture glides away from the emitters and toward the receivers, or viceversa. In particular, subsequent detections are compared, anddiscrimination is based on whether each detection pattern is becomingmore like type 1 or 3, or more like type 2 or 4.

Reference is made to FIG. 95, which is a simplified flowchart of amethod for determining the locations of simultaneous, diagonally opposedtouches, in accordance with an embodiment of the present invention. Atoperation 1031, two x-coordinates and two y-coordinates are detected,such as x-coordinates D1 and D2, and y-coordinates D3 and D4, shown inFIGS. 85 and 86. At operation 1032 the detected x-coordinates areanalyzed to identify a pattern of detection from among those listed inTABLE I. At operation 1033 the detected x-coordinates are rankedaccording to touches that occurred closer to or farther from adesignated screen edge, based on the pattern detected at operation 1032and based on the “Touch Location” column of TABLE I. The y-coordinatesrepresent distances from the designated edge. At operation 1034, eachranked x-coordinate is paired with a corresponding y-coordinate.Operations 1035-1037 are performed for the y-coordinates, similar tooperations 1032-1034 performed for the x-coordinates. At operation 1038,the two sets of results are compared.

Reference is made to FIG. 96, which is a simplified flowchart of amethod for discriminating between clockwise and counter-clockwisegestures, in accordance with an embodiment of the present invention. Atoperation 1041, two glide gestures are detected along an x-axis. Eachglide gesture is detected as a series of connected touch locations.Thus, with reference to FIGS. 85 and 86, a first glide gesture isdetected as a connected series of touch locations beginning atx-coordinate D1, and a second concurrent glide gesture is detected as aconnected series of touch locations beginning at x-coordinate D2. Atoperation 1042, the x-glide detections are analyzed to determine thetypes of detections that occurred in each series, from among thepatterns listed in TABLE I.

At operation 1043, the x-glide detections are ranked according totouches that occurred closer to or farther from a designated screenedge, based on the patterns of detections determined at operation 1042,and based on the “Touch Location” column of TABLE I. Operation 1043relates to series of connected touch detections over a time interval.Each series generally includes touch detections of patterns 1 and 3, orof patterns 2 and 4, listed in TABLE I, depending on whether the glidewas closer to or further away from the designated edge. In addition toanalyzing the individual detections that comprise a glide, the series oftouch detections is also analyzed to determine if the glide is movingcloser to or farther from the designated edge, based on comparison ofintensities of detections over time. E.g., in one series of detectionshaving multiple pattern 1 detections, if the amount of blocked lightincreases over time, then it is inferred that the glide is moving towardthe receivers, otherwise the glide is moving toward the emitters.

The y-coordinates represent distances from a designated edge, such asthe edge of emitters. At operation 1044 each ranked x-axis glide ispaired with a corresponding y-axis glide. Operations 1045-1047 areperformed for the y-axis glide, similar to operations 1042-1044performed for the x-axis glide. At operation 1048 the two sets ofresults are compared. At step 1049 a discrimination is made as towhether the rotation gesture is clockwise or counter-clockwise.

Calibration of Touch Screen Components

Reference is made to FIG. 97, which is a simplified flowchart of amethod of calibration and touch detection for an optical touch screen,in accordance with an embodiment of the present invention. In general,each emitter/receiver pair signal differs significantly from signals ofother pairs, due to mechanical and component tolerances. Calibration ofindividual emitters and receivers is performed to ensure that all signallevels are within a pre-designated range that has an acceptablesignal-to-noise ratio.

In accordance with an embodiment of the present invention, calibrationis performed by individually setting (i) pulse durations, and (ii) pulsestrengths, namely, emitter currents. For reasons of power consumption, alarge current and a short pulse duration is preferred. When a signal isbelow the pre-designated range, pulse duration and/or pulse strength isincreased. When a signal is above the pre-designated range, pulseduration and/or pulse strength is decreased.

As shown in FIG. 97, calibration (operation 1051) is performed at bootup (operation 1050), and is performed when a signal is detected outsidethe pre-designated range (operation 1055). Calibration is only performedwhen no touch is detected (operation 1053), and when all signals on thesame axis are stable (operation 1054); i.e., signal differences arewithin a noise level over a time duration.

Reference signal values for each emitter/receiver pair are used as abasis of comparison to recognize a touch, and to compute a weightedaverage of touch coordinates over a neighborhood. The reference signalvalue for an emitter/receiver pair is a normal signal level. Referencesignal values are collected at boot up, and updated when a change, suchas a change in ambient light or a mechanical change, is detected. Ingeneral, as shown in FIG. 97, reference signal values are updated(operation 1056) when signals are stable (operation 1054); i.e., whensignals are within their expected range for some number, N, of samplesover time.

A touch inside the touch area of a screen may slightly bend the screensurface, causing reflections that influence detected signal values atphoto diodes outside of the touch area. Such bending is more pronouncedwhen the touch object is fine or pointed, such as a stylus. In order toaccount for such bending, when a touch is detected (operation 1053), allstable signals (operation 1058) outside the touch area undergo areference update (operation 1059). When no touch is present and allsignals are stable (operation 1054), but a signal along an axis differsfrom the reference value by more than the expected noise level(operation 1055), the emitters are calibrated (operation 1051).Recalibration and updating of reference values require stable signals inorder to avoid influence of temporary signal values, such as signalvalues due to mechanical stress by bending or twisting of the screenframe.

To further avoid error due to noise, if the result of anemitter/receiver pair differs from a previous result by more than anexpected noise level, a new measurement is performed, and both resultsare compared to the previous result, to get a best match. If the finalvalue is within the expected noise level, a counter is incremented.Otherwise, the counter is cleared. The counter is subsequently used todetermine if a signal is stable or unstable, when updating referencevalues and when recalibrating.

After each complete scan, signals are normalized with their respectivereference values. If the normalized signals are not below a touchthreshold, then a check is made if a recalibration or an update ofreference values is necessary. If a normalized signal is below the touchthreshold, then a touch is detected (operation 1053).

To reduce risk of a false alarm touch detection, due to a suddendisturbance, the threshold for detecting an initial point of contactwith the screen, such as when a finger first touches the screen, isstricter than the threshold for detecting movement of a point ofcontact, such as gliding of a finger along the screen while touching thescreen. I.e., a higher signal difference is required to detect aninitial touch, vis-à-vis the difference required to detect movement ofan object along the screen surface. Furthermore, an initial contact isprocessed as pending until a rescan verifies that the touch is valid andthat the location of the touch remains at approximately the sameposition.

To determine the size of a touch object (operation 1057), the range ofblocked signals and their amplitudes are measured. For large objects,there is a wait for detecting an initial point of contact with thescreen, until the touch has settled, since the touch of a large objectis generally detected when the object is near the screen before it hasactually touched the screen. Additionally, when a large objectapproaches the screen in a direction not perpendicular to the toucharea, the subsequent location moves slightly from a first contactlocation.

However, objects with small contact areas, such as a pen or a stylus,are typically placed directly at the intended screen location. As such,in some embodiments of the present invention, the wait for detecting aninitial contact of a fine object is shortened or skipped entirely.

It has been found advantageous to limit the size of objects thatgenerate a touch, in order to prevent detection of a constant touch whena device with a touch screen is stored in a pouch or in a pocket.

At operation 1053, it is also necessary to distinguish between signalsrepresenting a valid touch, and signals arising from mechanical effects.In this regard, reference is made to FIG. 98, which is a picture showingthe difference between signals generated by a touch, and signalsgenerated by a mechanical effect, in accordance with an embodiment ofthe present invention. As seen in FIG. 98, signal gradients discriminatebetween a valid touch and a mechanical effect.

Reference is made to FIG. 99, which is a simplified diagram of a controlcircuit for setting pulse strength when calibrating an optical touchscreen, in accordance with an embodiment of the present invention.Reference is also made to FIG. 100, which is a plot of calibrationpulses for pulse strengths ranging from a minimum current to a maximumcurrent, for calibrating an optical touch screen in accordance with anembodiment of the present invention. FIG. 100 shows plots for sixdifferent pulse durations (PULSETIME1-PULSETIME 6), and sixteen pulsestrength levels (1-16) for each plot.

The control circuit of FIG. 99 includes 4 transistors with respectivevariable resistors R1, R2, R3 and R4. The values of the resistorscontrol the signal levels and the ratio between their values controlsgradients of the pulse curves shown in FIG. 99.

Reference is made to FIG. 101, which is a simplified pulse diagram and acorresponding output signal graph, for calibrating an optical touchscreen, in accordance with an embodiment of the present invention. Thesimplified pulse diagram is at the left in FIG. 101, and shows differentpulse duration, t₀, . . . , t_(N), that are managed by a control circuitwhen calibrating the touch screen. As shown in FIG. 101, multiplegradations are used to control duration of a pulse, and multiplegradations are used to control the pulse current. The correspondingoutput signal graph is at the right in FIG. 101.

As shown in FIG. 101, different pulse durations result in different risetimes and different amplitudes. Signal peaks occur close to the timewhen the analog-to-digital (A/D) sampler closes its sample and holdcircuit. In order to obtain a maximum output signal, the emitter pulseduration is controlled so as to end at or near the end of the A/Dsampling window. Since the A/D sampling time is fixed, the timing,t_(d), between the start of A/D sampling and the pulse activation timeis an important factor.

Assembly of Touch Screen Components

As described hereinabove, a minimum of tolerances are required whenaligning optical guides that after the shape of a wide light beam withrespective light emitters and light receivers, in order to achieveaccurate precision on an optical touch screen. A small misalignment canseverely degrade accuracy of touch detection by altering the light beam.It is difficult to accurately place a surface mounted receiver andtransmitter such that they are properly aligned with respective lightguides.

Because of this difficulty, in an embodiment of the present invention, alight guide and transmitter or receiver are combined into a singlemodule or optical element, as described above with reference to FIGS.49-52.

In some instances it may be of advantage not to combine an emitter or areceiver into an optical element, e.g., in order to use standard emitterand receiver components. In such instances precision placement ofcomponents is critical.

In some embodiments of the present invention, the optical lens thatincludes the feather pattern is part of a frame that fits over thescreen. FIG. 37 shows a cross-section of such a frame 455, which isseparate from LED 200.

Reference is made to FIG. 102, which is an illustration showing how acapillary effect is used to increase accuracy of positioning acomponent, such as an emitter or a receiver, on a substrate, inter aliaa printed circuit board or an optical component, in accordance with anembodiment of the present invention. Shown in FIG. 102 is an emitter ora receiver 398 that is to be aligned with an optical component ortemporary guide 513. Optical component or temporary guide 513 is fixedto a printed circuit board 763 by guide pins 764. Solder pads 765 areplaced at an offset from component solder pads 766. Printed circuitboard 763 is then inserted into a heat oven for soldering.

Reference is made to FIG. 103, which is an illustration showing theprinted circuit board 763 of FIG. 102, after having passed through aheat oven, in accordance with an embodiment of the present invention. Asshown in FIG. 103, component 398 has been sucked into place by thecapillary effect of the solder, guided by a notch 768 and a cavity 769in optical component or temporary guide 513. When a temporary guide isused, it may be reused for subsequent soldering.

The process described with reference to FIGS. 102 and 103 is suitablefor use in mass production of electronic devices.

The present invention has broad application to electronic devices withtouch sensitive screens, including small-size, mid-size and large-sizescreens. Such devices include inter alia computers, home entertainmentsystems, car entertainment systems, security systems, PDAs, cell phones,electronic games and toys, digital photo frames, digital musicalinstruments, e-book readers, TVs and GPS navigators.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will, however,be evident that various modifications and changes may be made to thespecific exemplary embodiments without departing from the broader spiritand scope of the invention as set forth in the appended claims.Accordingly, the specification and drawings are to be regarded in anillustrative rather than a restrictive sense.

1. A method of calibrating optical components in a light-based touchscreen, comprising: providing (i) a display, (ii) a row of light pulseemitters that sequentially transmit light pulses over the displayaccording to calibrated pulse current and pulse duration controls, and(iii) a row of light pulse receivers that receive the light pulses andthat output values representing the received light pulses, each receiverhaving expected values for emitter-receiver pairs when the light pulsesare not blocked; determining if each receiver output value for areceiver-emitter pair is within a respective designated range from thecorresponding receiver expected value; and when a receiver output valuefor a receiver-emitter pair is outside the designated range:recalibrating the emitter, comprising adjusting at least one of theemitter pulse current and pulse duration such that subsequent receiveroutput values are within the designated range; and updating the receiverexpected value for the receiver-emitter pair based on subsequent outputvalues of the receiver.
 2. The method of claim 1 further comprisingdetermining that light pulses are not being blocked based on thedeviation between receiver output values and expected values, prior tosaid recalibrating.
 3. The method of claim 2, wherein said determiningthat light pulses are not being blocked comprises comparing deviationsbetween receiver output values for neighboring emitter-receiver pairsand corresponding receiver expected values.
 4. The method of claim 1further comprising determining that receiver output values for theemitter-receiver pair are stable over a time duration, prior to saidrecalibrating.
 5. A method of updating receiver expected values in alight-based touch screen, comprising: providing (i) a display, (ii) arow of light pulse emitters that sequentially transmit calibrated lightpulses over the display, and (iii) a row of light pulse receivers thatreceive the light pulses and that output values representing thereceived light pulses, each receiver having expected values foremitter-receiver pairs when the light pulses are not blocked;determining which receivers detect a touch event on the display thatpartially blocks the light pulses, based on deviations between receiveroutput values for some receiver-emitter pairs, and correspondingreceiver expected values; and updating receiver expected values forremaining receiver-emitter pairs, based on corresponding receiver outputvalues.
 6. The method of claim 5 further comprising determining thatreceiver output values for the remaining receiver-emitter pairs arestable over a time duration, prior to said updating.
 7. The method ofclaim 5 further comprising determining that receiver output values forthe remaining receiver-emitter pairs are within a designated range oftheir expected values, prior to said updating.
 8. The method of claim 5,wherein said determining comprises comparing deviations between receiveroutput values for neighboring emitter-receiver pairs and correspondingreceiver expected values.